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  • richardmitnick 1:57 pm on March 19, 2019 Permalink | Reply
    Tags: "Life in the (low) background", Alan “Al” Smith, BLBF LBNL & SURF, SURF - Sanford Underground Research Facility, The science of low-background counting   

    From Sanford Underground Research Facility: “Life in the (low) background” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    March 15, 2019
    Erin Broberg

    Alan Smith set the gold standard for low background counting—a standard that guides the BLBF at Sanford Lab today.

    1
    Alan Smith (right) explains data recorded at the Oroville facility, where the first-generation dark matter and neutrinoless double-beta decay experiment was housed. Seated next to Smith is Dave Martinez, key account manager for AMETEK ORTEC. (Circa 1994.) Photo courtesy of Lawrence Berkeley National Laboratory.

    In 1953, Alan “Al” Smith arrived for his first day of work at Lawrence Berkeley National Laboratory (Berkeley Lab). Over the next seven decades, Smith advanced the science of low-background counting, working to push the capacity of detectors to see ever more minute signatures. He officially retired in 1994, but continued to come to the lab until 2018. By age of 92, Smith had created a “gold standard” of gamma-ray assay counting at Berkeley Lab and established a legacy within particle and nuclear physics research communities.

    “Al’s career has always been in the background of nuclear science—literally,” said Keenan Thomas, Nuclear Counting Facility Manager at Lawrence Livermore National Laboratory, who was previously mentored by Smith at Berkeley Lab as part of the Berkeley Low Background Facility (BLBF) team.

    Quieting the search

    Rare-event searches, such as the Majorana Demonstrator’s search for neutrinoless double-beta decay or LUX-ZEPLIN’s (LZ) dark matter hunt, don’t just need to be shielded from cosmic rays—they also require some of the world’s cleanest materials. By “clean,” researchers mean radio-pure; they are looking for materials with the lowest concentrations of radioactive elements.

    As radioactive elements such as uranium, thorium and potassium decay, they emit signals that quickly light up ultra-sensitive detectors and overwhelm rare-event signals. To lessen these misleading signatures, researchers use low-background counters (LBCs), which can detect even the tiniest amounts of radioactivity and assay all materials and components.

    “Low-background counting is a tedious, yet critical, quality-control step toward success of rare-event experiments,” said Thomas. “Low-level assays are one of our last lines of defense to ensure that an experiment will be successful in achieving the sensitivity to the very weak signals it was designed for—and not be masked by spurious background signals generated from many different sources, including the materials in the detector itself.”

    Going deeper for science

    Smith’s career both paralleled and propelled advances in low-background counting. When Smith began his work in the 1950s, nuclear science was relatively new and booming, with many measurements yet to be made. The Bevatron particle accelerator came online at Berkeley Lab in 1954, and Smith was initially tasked with assessing the stray neutrons it produced.

    LBNL Bevatron

    To do this, he placed large aluminum discs called “activation foils” around the perimeter of the Bevatron to “capture” neutrons that scattered from the accelerator. By assaying these foils later with sodium iodide detectors, Smith determined the amount of neutrons produced using weak signals from the trace amounts of radioactivity generated in the foils.

    3
    Smith places an aluminum disk sample exposed to radiation at the Bevatron into a lead and concrete box containing a detector at the low-level radiation counting facility, circa 1950s.
    Photo courtesy of Lawrence Berkeley National Laboratory

    Smith realized that the Bevatron itself created a dynamic background, which clouded the measurements. To reduce this noise, a low background “cave” was constructed using a single pour of concrete, with walls ranging from 4-6 feet thick. Smith and a graduate student, Harold Wollenberg, carefully counted dozens of samples of concrete source materials to find a supply with the lowest levels of naturally occurring radioactive elements. The dense walls reduced external backgrounds from the Bevatron, cosmic rays and natural radioactivity in the environment—all with the benefit of not emitting a significant amount of background themselves. This cave became the surface location for the Berkeley Low Background Facility (BLBF) and is still in use today.

    In the 1980s, Smith became involved with the University of California-Santa Barbara and Berkeley Lab double-beta decay experiment, which used high-purity germanium detectors. Originally installed in the low-background cave at Berkeley Lab, researchers soon realized the backgrounds from cosmic rays were still too high. Smith turned to his professional connections at the underground Hyatt Power Plant at Oroville Dam, to secure a space for the experiment to relocate a few hundred feet below ground. The underground space supplied sufficient overburden for the experiment, and transitioned into a remote location that housed low-background counters for BLBF for decades.

    In 2014, the BLBF at Oroville was relocated to the Black Hills State University Underground Campus (BHUC) on the 4850 Level of Sanford Lab. Before the move, Smith assayed hundreds of samples from the 4850 Level, including natural rocks, concrete, shotcrete, paint and other materials to determine what kinds of backgrounds existed. His attention to these samples from the underground construction of the Davis Campus created ample material-radiopurity data that researchers now use in simulations for Sanford Lab experiments. Once the transition to BHUC was completed in 2015, Smith and his team received and analyzed data online at Berkeley Lab.

    Today, the BLBF performs low background counting in its two unique facilities—the surface site at Berkeley Lab and the underground site at Sanford Lab. Researchers assaying their materials from a distance can monitor results in real-time, while relying on daily support from BHSU faculty and students and Sanford Lab staff. Support includes changing samples in the detectors, monitoring the liquid nitrogen systems that purge radon from inside the detectors and assistance in the installation of detectors underground.

    “The campus at Sanford Lab is an ideal location for these counters,” said Kevin Lesko, senior scientist at Berkeley Lab. “Not only does its depth create a shield for the detectors, but it’s in the thick of major physics experiments—it’s where the action is.”

    Both facility locations owe much of their design and creation to Smith’s meticulous measurements.

    Creating a “gold standard”

    Throughout his career, Smith pushed the capabilities of low-background counting, striving to make more and more sensitive measurements. As technology advanced, his methods of detection graduated from sodium iodine (NaI), to germanium lithium-drifted (GeLi) and eventually to high-purity germanium detectors (HPGe). With each advancement, his methods became more sensitive and intrinsic backgrounds needed to be reduced even further. Reducing backgrounds necessitated knowledge in the natural radioactivity of common materials used in the shielding and detectors themselves.

    As he measured countless materials for various projects, Smith developed a deep expertise that became crucial to research into neutrinos, neutrinoless double-beta decay and dark matter—experiments that required extreme radiopurity in detector materials to detect extremely rare, weakly-interacting signals.

    His vast knowledge of the backgrounds in common materials, including metals, composites and ceramics, brought many researchers at Berkeley Lab to him first when designing experiments. Researchers would ask what they should use to create a component of their experiment, and Smith would quickly point them toward the materials with the lowest levels of natural radioactivity.

    3
    Smith displaying the Michael Nitschke Award for Technical Excellence he received in 2001. Photo courtesy of Lawrence Berkeley National Laboratory.

    “We have immense trust in Al’s judgement,” said Alan Poon, deputy director of the Berkeley Lab Nuclear Science Division, who worked with Smith on multiple projects, including the design and construction of the Majorana Demonstrator detector. “Looking at the counting data from a sample, he could sometimes give us an entire history of the material and the impact it would make on our experiment.”

    When Smith left Berkeley Lab in 2018, he had contributed to dozens of high-profile physics experiments—including Nobel Prize-winning SNO, KATRIN, the Daya Bay Reactor Neutrino Experiment, LUX [see below], LZ [see below], Majorana [see below], CUORE, DM-Ice, LBNE (the precursor to LBNF/DUNE [see below]), Double Chooz, KamLAND, and more—all while living in the background.

    SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario

    KIT Katrin experiment

    Daya Bay, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China

    CUORE experiment,at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS) in Italy,a search for neutrinoless double beta decay

    Double-Chooz – Two identical detectors are to be installed near the Chooz nuclear power plant, in the French Ardennes, at different distances from the reactors

    KamLAND-Zen detector, an electron antineutrino detector at the Kamioka Observatory, an underground neutrino detection facility near Toyama, Japan

    “I don’t think we would have achieved what we did without Al’s work,” said Poon. “He set the gold standard for low-background counting.”

    Looking forward

    Sanford Lab benefits tremendously from the impacts of Smith and his team. His scrupulous records of underground backgrounds inform researcher’s simulations, while the materials he screened are part of the the Majorana Demonstrator and LZ dark matter detectors.

    Most notably, his influence is seen at the BLBF on the 4850 Level, where six low-background counters quietly collect data using high-purity germanium detectors.

    BLBF LBNL& SURF

    Here, the same detectors once used for measuring materials for LUX and the Majorana Demonstrator will continue counting for next-generation experiments, including LZ, LEGEND and the Deep Underground Neutrino Experiment.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.

    LBNL LZ project at SURF, Lead, SD, USA

    LBNL LZ project will replace LUX at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    FNAL LBNE/DUNE from FNAL to SURF, Lead, South Dakota, USA


    LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA

    CASPAR at SURF


    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”

     
  • richardmitnick 11:51 am on March 12, 2019 Permalink | Reply
    Tags: "What are cosmic rays?", As Hess ascended 5300 meters he measured the rate of ionization in the earth’s atmosphere finding it increased by three times the amount at sea level., , , At SURF LUX-ZEPLIN (LZ) which is searching for dark matter and the MAJORANA DEMONSTRATOR which seeks to better understand the properties of neutrinos build additional shielding to block out the rest., , Cosmic rays were first discovered in August 1912 by Austrian physicist Victor Hess on an historic balloon flight., , SURF - Sanford Underground Research Facility   

    From Sanford Underground Research Facility: “What are cosmic rays?” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    March 11, 2019
    Constance Walter

    1
    Sandbox Studio, Chicago

    At Sanford Underground Research Facility, we talk a lot about cosmic rays and the need to escape them—not because they are harmful to humans, but because they create background noise in sensitive physics experiments that are seeking very rare physics events.

    So, what are cosmic rays, exactly, and why the need to escape them?

    Cosmic rays were first discovered in August 1912 by Austrian physicist Victor Hess on an historic balloon flight. As Hess ascended 5,300 meters, he measured the rate of ionization in the earth’s atmosphere, finding it increased by three times the amount at sea level.

    The term ‘cosmic rays’ is a misnomer. They’re really particles—mostly protons—that hurtle through space at nearly the speed of light. When they arrive at our little rock, they collide with the nuclei of other atoms in the upper atmosphere, creating even more particles that then shower the earth (one or two pass through your hand unimpeded every second). To escape these ubiquitous particles, researchers build physics experiments deep underground.

    At Sanford Lab, the rock overburden stops most of the cosmic radiation before it reaches the experiments on the 4850 Level. Still, LUX-ZEPLIN (LZ), which is searching for dark matter, and the MAJORANA DEMONSTRATOR, which seeks to better understand the properties of neutrinos, build additional shielding to block out the rest.

    In a 2017 paper [Science], MAJORANA reported that the depth of the experiment in conjunction with its extraordinary shielding efforts had paid off.

    “We know that we created an environment that is incredibly clean and quiet,” said Vincente Guiseppe, co-spokesperson with MAJORANA. “Our initial results give us a better understanding of the always-elusive neutrino and how it shaped the universe.”

    But some researchers don’t want to avoid cosmic rays—they want to understand them. According to NASA, understanding the chemical composition of cosmic rays is important because they are direct samples of matter from outside the solar system and contain rare elements and they can provide important information on the chemical evolution of the universe.

    Dr. Mike Cherry, the Roy P. Daniels Professor of Physics at Louisiana State University, studied very energetic cosmic rays nearly a mile underground at the Homestake Mine (now the Sanford Underground Research Facility) in Lead, South Dakota, from 1980 to 1988.

    “We wanted to find out the source of these rare, very energetic cosmic events,” Cherry said.“High-energy cosmic rays are the rarest form and could come from exploding stars, which may also emit gamma-ray bursts.”

    Cherry installed the Large Area Scintillation Detector (LASD)—an array of 200 one-foot square plastic pipes welded together and stacked around Ray Davis’ solar neutrino tank. The pipes contained ultra-pure mineral oil and had sensitive light detectors on each end. In conjunction with an array of air shower detectors on the surface, Cherry hoped to draw a line between cosmic ray events on the surface and underground. He continues to do research in the field.

    A Black Hills cosmic connection

    Balloon flights from the 1930s through the mid-1960s—some of which took place from the Stratobowl in the Black Hills of South Dakota—continued to measure both high- and low-energy cosmic radiation. The flights also gathered meteorological and other scientific data necessary to improve safety at high altitudes.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis.

    LBNL LZ project at SURF, Lead, SD, USA

    LBNL LZ project will replace LUX at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    FNAL LBNE/DUNE from FNAL to SURF, Lead, South Dakota, USA


    LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA

    CASPAR at SURF


    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”

     
  • richardmitnick 12:06 pm on February 26, 2019 Permalink | Reply
    Tags: , , LBNL LZ- LUX-ZEPLIN experiment at SURF, SURF - Sanford Underground Research Facility, The LZ collaboration will circulate liquid xenon through the test cryostat to ensure the system will work properly when the experiment begins operations next year   

    From Sanford Underground Research Facility: “LZ begins new phase: testing the xenon circulation system” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    February 25, 2019
    Constance Walter

    Test will ensure critical element of the next-generation dark matter experiment will operate as needed.

    1
    David Woodward, a researcher on the LZ experiment, works on the test cryostat. Photo by Claudio Pascoal da Silva

    In preparation to test the xenon circulation system for the LUX-ZEPLIN (LZ) dark matter experiment, David Woodward carefully positioned a tower holding a stainless-steel test cryostat. The LZ collaboration will circulate liquid xenon through the test cryostat to ensure the system will work properly when the experiment begins operations next year.

    LBNL LZ project at SURF, Lead, SD, USA

    “We aren’t looking for dark matter with this test. But we do want to make sure all of our systems work the way they are supposed to,” said Woodward, a post doc at Penn State University.

    The circulation system is, perhaps, the most critical component of the LUX-ZEPLIN dark matter experiment. LZ will use 10 tons of liquid xenon to look for WIMPs—weakly interacting massive particles—and that xenon must meet very high radio-purity standards to eliminate background noise. To achieve and maintain this level of radiopurity, the xenon must be continuously removed, purified and reintroduced to the LZ detector, or circulated, during operation.

    The circulation system sits outside the water tank, which will house LZ. It’s a complicated system comprised of thousands of components: circulation compressors, tubing, wiring, sensors, all of which will connect to the actual experiment. The inner cryostat will hold the xenon, which will be fed into the experiment through an opening at the bottom of the water tank then continuously circulated.

    The test cryostat is designed very much like the real inner cryostat. It is the same height and has many of the same components; however, it is not as big around.

    “One of the goals of the test is to make sure we can circulate the xenon at the correct rate,” Woodward said. “That’s definitely possible even with a test device that isn’t exactly the same size as the actual device. It helps us understand whether the flow will work correctly—to make sure we can get the xenon to circulate all the way to the top of the actual cryostat,” Woodward added.

    The tower holding the test cryostat was positioned precisely to ensure the xenon transfer lines, which have a fixed length, will reach the real LZ cryostat once the experiment is actually running. The collaboration will monitor the system; however, there are some things they won’t be able to know, unless they can physically look inside the test cryostat. To do that, they added a glass view port on the top of the device.

    Why do they need a viewport?

    “The xenon has to stay at a certain temperature to remain liquid (minus 169.2 degrees F),” Woodward said. “If it doesn’t stay cold enough, it can revert back to gas. Gas creates bubbles, so if that happened, we could see the bubbles. But, really, we don’t want to see anything—we want this test to be boring and just see a nice flow of the liquid xenon. But if something did happen, we could see it.”

    The team will test the circulation system for several months, or as long as possible, Woodward said, to ensure it is working correctly. Then the test cryostat will be unhooked and removed. By end of summer this year, the actual cryostat will be installed, with operation of the experiment expected to begin in early 2020.

    “This test is very important to our experiment, a very important check for the next phase,” Woodward added.

    Facts and figures

    The test cryostat is made of stainless steel, whereas the one that will be used in the experiment is made of titanium. Although it is as tall as the actual cryostat, it is much smaller in diameter. “We are not looking to collect physics data with the test vessel, so we don’t need the volume,” said Woodward.

    In building the test vessel, the team followed fairly closely the cleanliness protocols for the actual vessel that will be used. It’s important that we have the purest materials possible to minimize radioactive backgrounds in the actual experiment. “We don’t want this test to dirty the real circulation system, so we had to construct it inside the surface clean room then seal it up before bringing it underground,” Woodward said.

    The test cryostat arrived from Penn State where it was initially assembled inside a cleanroom. At Sanford Lab, the test cryostat was cleaned and prepared for use underground. Now, it is underground where it is being used to test the circulation system. “That’s how we’ll know if the system is working.”

    By the numbers:

    100 inches: The height of the inner cryostat
    10 feet: The height of the outer cryostat
    10 tons: The amount of liquid xenon that will be used inside the inner cryostat
    70 kg: The amount of liquid xenon used to test the circulation system

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
    LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

    LBNL LZ project will replace LUX at SURF [see below]

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE
    LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA

    CASPAR at SURF


    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”

     
  • richardmitnick 5:27 pm on February 20, 2019 Permalink | Reply
    Tags: , , , , , Photo Essay- Underground Lab science in many fields, , SURF - Sanford Underground Research Facility   

    From Sanford Underground Research Facility: “Science impact” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    2.20.19
    Erin Broberg
    Matthew Kapust, photographer

    Sanford Lab’s dedication to science, research and development and engineering, as well as its innovative approach to education, make it a world-leading science facility.

    1
    Dark matter science impacts

    The LZ experiment is the upgraded successor to the highly successful Large Underground Xenon (LUX) experiment. LUX held world-leading sensitivity for approximately three and a half years over most of the WIMP-mass region. The LZ experiment was one of two direct-search, next-generation dark matter experiments selected for funding by DOE’s Office of High Energy Physics (HEP).

    LZ involves a collaboration of 250 scientists, engineers and technicians from 38 institutions, including five U.S. National Labs. LZ expects to achieve a projected sensitivity level up to 100 times better than the final LUX search result for weakly interacting massive particles (WIMPs), the leading dark matter particle candidate.

    Currently in the construction and installation phase, LZ is expected to begin operations in late 2019. The collaboration will perform a direct search for dark matter using 10 tonnes of liquid xenon within an ultra-pure titanium cryostat that will be surrounded by a new liquid scintillator veto system. The entire experiment will be immersed in a 72,000-gallon tank filled with ultra-pure water.

    7
    Neutrino science impacts

    Beginning with Dr. Ray Davis’ groundbreaking neutrino research (1965-1992), the drifts at Sanford Lab are dedicated to refining knowledge about neutrinos and other research.

    The Majorana Demonstrator Project has been collecting physics data since 2017. Recently published results are competitive with world-leading experiments and highlight the exceptional energy resolution and low backgrounds that have been achieved through the shielding offered at Sanford Lab.

    The MJD project invested significant resources to produce the world’s purest copper. In parallel with ongoing MJD operations, specific elements—such as electronics upgrades and copper electroforming—are being pursued at Sanford Lab in the context of R&D for the next-generation neutrinoless double-beta decay experiment called the Large Enriched Germanium Experiment for Neutrinoless bb Decay (LEGEND). LEGEND-200 physics data collection is expected to begin in 2021. Extraordinary levels of material radiopurity will be required to reach the LEGEND-1000 background goal.

    The work done at Sanford Lab, including depth and ultra-pure materials, have been instrumental in refining the search and preparing for the next generations.

    223 acres
    Surface footprint
    9

    The local footprint of the facility includes 223 acres on the surface. Facilities at both the Yates and Ross surface campuses offer researchers administrative support, office space, communications and education and public outreach. The Waste Water Treatment Plant handles and processes waste materials and a warehouse for shipping and receiving.

    370 miles
    Underground footprint
    10
    Of the 370 total miles of underground space, Sanford Lab maintains approximately 12 for science at various levels, including the 300, 800, 1700, 2000, 4100, and 4850 levels. The Davis Campus on the 4850 Level is a world-class laboratory space that houses experiment for neutrinoless double-beta decay and dark matter.

    The CASPAR experiment, led by SD Mines, studies stellar nuclear fusion reactions, especially neutron production for slow neutron-capture nucleosynthesis (s-process). Accelerator components were relocated from the University of Notre Dame in 2015, and since the first beam in May 2017 and the first operations event in July 2017, accelerator commissioning has continued. Advanced commissioning data were obtained starting in February 2018 using the domain of interest for stellar CNO reactions.

    “Researchers at CASPAR are engaging a community of researchers. Although Notre Dame and SD Mines are at the core, the collaboration continues to reach out to other research groups to build interest. One of the biggest impacts in South Dakota is the number of grad students participating in the Physics Ph.D. program in the state.” —Jaret Heise

    CASPAR at SURF

    12
    Low-background counting impacts

    The BHUC houses a low-background counting facility where components for physics experiments, including current and future Sanford Lab experiments, can be assayed. There has been significant interest in the BHUC low-background counting facility from many groups, including the Sub Electron Noise Skipper-CCD Experimental Instrument (SENSEI) experiment, which aims to search for low-mass dark matter using ~100 g of silicon CCD sensors, and the Germanium Internal Charge Amplification for Dark Matter Searches (GeICA) project.

    Six high-purity germanium detectors are currently operating at the facility, with installation of an additional germanium detector expected in 2019. These low-background counters have been instrumental in characterizing materials for the LZ experiment for the past several years.

    “The campus at Sanford Lab is an ideal location for these counters. Not only does its depth create a shield for the detectors, but it’s in the thick of major physics experiments—it’s where the action is.” —Kevin Lesko, senior scientist at Lawrence Berkley National Lab (Berkeley Lab) who manages the measurement and control of backgrounds

    13
    Geology research impacts

    The SIGMA-V experiment, led by Lawrence Berkeley National Lab (Berkeley Lab), is a significant effort within the earth science field. SIGMA-V mobilized in October 2017, drilling a set of eight horizontal holes (each nearly 200 feet long) on the 4850L.

    Members of the SIGMA-V experiment are continuing to explore enhanced or engineered geothermal systems (EGS) by building on results obtained from a previous experiment that was hosted at SURF between 2016 and 2017. Both groups drilled new holes as field demonstration sites in support of DOE flagship EGS effort called the Frontier Observatory for Research in Geothermal Energy (FORGE). SIGMA-V is testing the validation of thermal-hydrological mechanical-chemical (THMC) modeling approaches, as well as novel monitoring tools.

    4
    Biology opportunities

    Important questions in life science, such as the conditions of life, the extent of life and ultimately the rules of life, are also being addressed underground at SURF. Generally, these programs have a small footprint in existing spaces and require only modest support from the facility. Biology researchers take full advantage of SURF’s footprint by gathering samples from a number of underground levels and areas with different temperatures and geologic mineralogies. Various groups focus on the diversity of life, including rock-hosted microbial ecosystems, and engineering applications such as improvements to biofuel production.

    15
    Engineering

    The Sanford Underground Research Facility offers a variety of environments in which engineers can test real-world applications and new technologies. And the rich history of the Homestake Mine, which includes a vast archive of core samples, allows engineers to better understand how to excavate caverns for new experiments.

    Sanford Lab’s dedication to science, research and development and engineering, as well as its innovative approach to education, make it a world-leading science facility.

    The Sanford Underground Research Facility supports world-leading research in particle and nuclear physics and other science disciplines. While still a gold mine, the facility hosted Ray Davis’s solar neutrino experiment, which shared the 2002 Nobel Prize in Physics. His work is a model for other experiments looking to understand the nature of the universe.

    The Facility’s depth, rock stability and history make it ideal for sensitive experiments that need to escape cosmic rays. The impacts on science can be seen worldwide.

    2
    Our science as national priority

    In 2014, the Department of Energy’s High Energy Physics Advisory Panel (HEPAP) committee prioritized physics experiments, giving neutrino and dark matter projects high-priority. Sanford Lab houses two of the five experiments named in the Particle Physics Project Prioritization Panel (P-5) Report: LUX-ZEPLIN (LZ) and LBNF/DUNE.

    In 2015, a similar report done by the Department of Energy’s Nuclear Science Advisory Committee (NSAC) committee prioritized the ton-scale neutrinoless double-beta decay experiment, which aligns with the objectives of the Majorana Demonstrator Project.

    3
    International investment and cooperation

    Sanford Lab hosts a variety of research projects in many disciplines. Researchers from around the globe use the facility to learn more about our universe, life underground and the unique geology of the region.

    The site also allows scientists to share and foster growth within the science community and encourages cooperation between many countries and institutions.

    We now have several hundred researchers from dozens of institutions around the world.

    For example, for the first time in its history, CERN is investing in an experiment outside of the European Union with its $90 million commitment to LBNF/DUNE in the form of ProtoDUNE. The ProtoDUNE detectors have already recorded physics results. Additionally, the UK committed $88 million to the project.

    CERN ProtoDune

    Cern ProtoDune

    4

    Local impact

    Building laboratory spaces deep underground at Sanford Lab created new opportunities for higher education in South Dakota. In 2012, the Board of Regents authorized a joint Ph.D. physics program at the South Dakota School of Mines and Technology in Rapid City and the University of South Dakota in Vermillion. Since then, dozens of students have participated in the program and worked on experiments at Sanford Lab. In 2017, each university saw their first students complete the program.

    To date, there are 27 ongoing research projects housed at Sanford Lab, 24 of which include students and faculty from universities across South Dakota.

    The Black Hills State University Underground Campus (BHUC) provides a space for students from across the state to preform interdisciplinary research underground. While physics students contribute to large-scale physics experiments by working in the low background counting facility, students from other disciplines can work on research in two areas adjoining the counting cleanroom.

    “Biology students can study microbes in situ, and geology students can study the unique rock formations of the Black Hills,” said Briana Mount, director of the BHUC.

    Additionally, a National Science Foundation (NSF) program, Research Experience for Undergraduates (REU), gives students from around the country, opportunities to pursue research through the underground campus.

    5

    Global footprint

    Competition for underground laboratory space is fierce. With the completion of the Long-Baseline Neutrino Facility (LBNF) construction, Sanford Lab will host approximately 25 percent of the total volume of underground laboratory space in the world.

    Surf-Dune/LBNF Caverns at Sanford


    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA

    The sheer amount of space (7,700 acres underground) and existing infrastructure make the site highly attractive for future experiments in a variety of disciplines.

    Global footprint depth

    Sanford Lab is the deepest underground lab in the U.S. at 1,490 meters. The average rock overburden is approximately 4300 meters water equivalent for existing laboratories on the 4850 Level. The underground laboratory space has a strong track record of meeting experiment needs.

    6

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
    LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

    LBNL LZ project will replace LUX at SURF [see below]

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE
    LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA

    CASPAR at SURF


    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”

     
  • richardmitnick 11:36 am on February 14, 2019 Permalink | Reply
    Tags: , , , , , SURF - Sanford Underground Research Facility   

    From Sanford Underground Research Facility: “Enhancing the search” 

    SURF logo
    Sanford Underground levels

    2.13.19
    Erin Broberg

    Photos by Matt Kapust

    From Sanford Underground Research Facility

    Changes in LUX’s design optimize LZ’s search for dark matter.

    1

    2
    LUX cryostat

    To increase the amount of xenon atoms in a given volume, scientists cool xenon gas to very low temperatures until it becomes liquid. To keep the experiment cold, it is housed in a double-walled titanium vessel to maintain the low temperature, a cryostat. The LUX cryostat held 380 kg of LXe.

    The LUX cryostat held 380 kilograms of liquid xenon.

    3
    LZ cryostat

    LZ will hold 10 tons of liquid xenon, over 26 times the volume previously contained by LUX. This increases the chances for a WIMP to collide with a xenon atom, causing a series of signatures to be detected.

    4
    LUX PMTs

    Essential to the detection of WIMP signatures are two arrays of photomultiplier tubes (PMTs), housed at the top and bottom of the cryostat.

    The arrays in LUX held a combined 122 PMTs, each with a two-inch diameter.

    5
    LZ PMTs

    With a larger volume of xenon to monitor, researchers have designed larger PMT arrays. LZ will boast a total of 494 PMTs, three inches in diameter, in the top and bottom arrays.

    To optimize both their detection and veto capabilities, researchers have included additional PMTs in the skin and dome structures of the detector.

    6

    “In addition to the size, we are improving every aspect of the experiment that we can,” Horn said.

    To transport and store the xenon, LUX previously used eight compressed gas cylinders. LZ will use 200 of these cylinders stored in a newly outfitted room outside the laboratory underground.

    More xenon means a larger, more complex circulation system. Previously, the pumps exchanged 25 liters of purified xenon gas per minute. The small pumps will be replaced with large compressors capable of circulating xenon efficiently. Now, that number will be closer to 200 liters per minute.

    A xenon tower outside the water tank will allow xenon to be heated to its gaseous form, purified, then re-liquified before it is reintroduced into the detector again.

    The signal readouts for all photomultipliers and sensors amount to over 1000 cables which will run out of the detector and into computer racks. Also, the voltages required to create the electric field over the increased detector size are significantly higher.

    “Overall, there are far more challenges, more sub-systems and simply far more pieces to this experiment – all bigger and better than before”, said Horn.

    7
    Increasing veto detection

    LUX relied on the water tank as a veto detector, helping researchers rule out extraneous signatures.

    In addition to the water tank, LZ will improve veto detection by installing nine acrylic vessels around the cryostat, filled with a liquid scintillator and and monitored by larger PMTs (8-inch diameter) within the water tank. This system allows researchers to further reduce backgrounds by by observing interactions outside the detector.

    In 2013, the Large Underground Xenon detector (LUX) at Sanford Underground Research Facility (Sanford Lab) was named the most sensitive dark matter detector in the world. In the global search for Weakly Interacting Massive Particles (WIMPs), a candidate for dark matter, LUX was preforming exceedingly well.

    So why did the collaboration decommission LUX in 2016? And why are they building a larger detector—LUX-ZEPLIN (LZ)—in it’s place?

    “The search for dark matter is a numbers’ game,” said Markus Horn, Sanford Lab research scientist and member of the LZ collaboration. “We’re waiting for a dark matter particle or weakly interacting massive particle (WIMP) to interact with the xenon atoms in the detector. The likelihood of such an interaction depends on how many xenon atoms we have.”

    By sizing up the experiment, researchers increase their chances of witnessing rare WIMP interactions with a larger volume to hold xenon. Horn said that, while the size of the detector isn’t the only way researchers are enhancing the search, it’s a good starting point.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
    LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

    LBNL LZ project will replace LUX at SURF [see below].

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE
    LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA

    CASPAR at SURF


    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”

     
  • richardmitnick 2:03 pm on February 5, 2019 Permalink | Reply
    Tags: A new source for Majorana calibration, , Cobalt-56 is an ideal source-Cobalt-56 has a really short half-life only 77 days, , , , SURF - Sanford Underground Research Facility, The collaboration has been using its thorium source for five years- the signatures it produces are at a slightly higher energy level than that at which neutrinoless double-beta decay is expected to oc, Thorium lasts for years. Indeed the collaboration has been using its thorium source for five years,   

    From Sanford Underground Research Facility: “A new source for Majorana calibration” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    February 4, 2019
    Erin Broberg

    Researchers recently got a special delivery: a hundred million atoms of Cobalt-56, an ideal calibration source.

    1
    A string of germanium detectors inside a cleanroom glovebox on the 4850 Level of Sanford Lab, before they were installed in the Majorana Demonstrator in 2016.
    Photo by Matthew Kapust

    U Washington Majorana Demonstrator Experiment at SURF

    Researchers have not seen the copper glow of the Majorana Demonstrator’s internal detector since 2016. Sealed behind six layers, including 5,200 lead bricks and two heavy copper shields, the Majorana Demonstrator has recorded a steady stream of data that will inform the next-generation neutrinoless double-beta decay experiments. But how do researchers know if the information they’re receiving is accurate? How do they know something hasn’t gone amiss deep inside?

    Simple. They use an advanced calibration system that allows them to monitor the performance of the germanium detectors that make up the heart of the demonstrator. Ralph Massarczyk, staff scientist at Los Alamos National Laboratory, designed and created the calibration system used by the Majorana Demonstrator collaboration.

    “In a typical detector,” Massarczyk explains, “there is enough natural background that you can easily calibrate a detector. But with Majorana, you have a very minimal background, which is not enough to determine its performance.”

    Without substantial background data, researchers don’t know if the background is stable or not. The detector could be reporting events at inaccurate energy levels or even missing them completely. So, to calibrate this extremely sensitive detector, a calibration source is used to produce a standard set of well-known physics events that researchers can use to understand detector performance.

    Typically, the collaboration uses thorium, a naturally occurring, slightly radioactive material that creates signatures the Majorana Demonstrator can easily read. The only problem with this source is that the signatures it produces are at a slightly higher energy level than that at which neutrinoless double-beta decay is expected to occur.

    For a more ideal calibration, Massarczyk and his team got a special delivery: a hundred million atoms of Cobalt-56, a slightly radioactive isotope created in particle accelerators and used mostly in the medical field. The source underwent several “swipe tests” to ensure no leaks had occurred.

    “Cobalt-56 is an ideal source. It produces a lot of events, and those events are at the exact energy where we expect to see a neutrinoless double-beta decay event,” Massarczyk said.

    If it is such a perfect indicator, why don’t researchers use it every time?

    “Cobalt-56 has a really short half-life, only 77 days,” said Massarczyk. “This means that at the end of 77 days, only one-half of the source will be left. After waiting another 77 days, only one-fourth will be left. After a year, the source is gone.”

    Thorium, on the other hand, lasts for years. Indeed, the collaboration has been using its thorium source for five years, Massarczyk said.

    Delivery methods

    To deliver a calibration source to the detector modules behind layers of shielding, Massarczyk designed a “line source.” In this system, a 5-meter long, half-inch thick plastic tube is inserted into a track from the outside of the shield. The tube, which carries the calibration source, is pushed along the “grooves” on the outside of each detector module, snaking its way around twice.

    “It sort of resembles a helix,” Massarczyk said. “This way, the signals are distributed evenly, rather than coming from one point, allowing each detector within the modules to see activity from the same source.”

    The normal rate for the Majorana Demonstrator is a few signature counts per hour. When a radioactive calibration source is included, researchers see a few thousand events per second. During its weekly calibration run, the Majorana Demonstrator sees more events in 3 hours than it would otherwise detect in the span of 120 years.

    “If, while this source is inside, the demonstrator creates signals that correspond with known data, then we know the demonstrator is well-calibrated and on track,” Massarczyk said.

    Looking to the future

    The Majorana Demonstrator is expected to run for a few more years, so the short half-life of Cobalt-56 means it is not a sustainable calibration option for the team. That’s why this week’s calibration was so important. The data collected has been sent to analysts for interpretation.

    “The main purpose for this data is to double-check the data analysis we do in the energy region 2MeV, where we expect the neutrinoless double-beta decay events to occur,” Massarczyk said.

    The information gained from these tests also is of interest to collaborators with LEGEND (Large Enriched Germanium Experiment for Neutrinoless ββ Decay), who are trying to perfect the next-generation neutrinoless double-beta decay experiment.

    Legend Collaboration UNC Chapel Hill

    “As they plan a ton-scale experiment, researchers want to know if the materials are clean enough, if the shielding is working and how far underground they need to go,” said Massarczyk. “Understanding the backgrounds gives us important information to make those decisions.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
    LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE
    LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA

    CASPAR at SURF


    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”

     
  • richardmitnick 12:48 pm on January 22, 2019 Permalink | Reply
    Tags: , , SURF - Sanford Underground Research Facility   

    From Sanford Underground Research Facility: “LZ gets an eye exam” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    January 18, 2019
    Erin Broberg

    1
    Brown University graduate student Will Taylor attaches data collection cables to a section of the PMT array. Matthew Kapust

    Lights out, windows darkened, doors closed. It’s not after hours at the Surface Assembly Lab (SAL), it’s just time for the first of LUX-ZEPLIN (LZ) dark matter detector’s on-site eye exam.

    LZ’s “eyes” are two massive arrays of photomultiplier tubes (PMTs), powerful light sensors that will detect any faint signals produced by dark matter particles when the experiment begins in 2020. The first of these arrays, which holds 241 PMTs, arrived at Sanford Underground Research Facility (Sanford Lab) in December. Now, researchers are testing the PMTs for the bottom array to make sure they are still in working condition after being transported from Brown University, where they were assembled.

    “These PMTs have already undergone rigorous testing, down to their individual components and this is the final test after transport to the site,” said Will Taylor, a graduate student at Brown University who has been working with the LZ collaboration since 2014.

    Once testing is completed, the bottom PMT array will be placed in the inner cryostat. The same process will be followed for the top array. The inner cryostat will be filled with xenon, both gaseous and liquid, and placed in the outer cryostat. Then, the entire detector will be submerged in the 72,000-gallon water tank in the Davis Campus on the 4850 Level of Sanford Lab.

    “As you can imagine,” Taylor said. “It will be impossible to change out a faulty PMT after the experiment is completely assembled. This is our last chance to ensure each PMT is working perfectly.”

    While researchers do expect a few PMTs to “blink out” over LZ’s five to six year lifetime, only the best of the best will make it into the detector. So, just how do researchers transform the SAL into an optometrist’s office?

    Royal treatment

    First, the array is placed in a special enclosure called the PALACE (PMT Array Lifting And Cleanliness Enclosure). There, the PMTs are shielded from light and dust. This enclosure also allows researchers access to the PMTs through a rotating window and to connect data collection systems to different sections of PMTs at a time.

    “We test by section, collecting data from 30 PMTs per day,” said Taylor. “Each individual PMT has a serial number and is tagged to its own data, so we know exactly what each PMT is ‘seeing.’”

    Going dark

    For the first test, researchers look at what is called the “dark rate” of each PMT. To perform this test, researchers seal up the PALACE, turn off the lights in the cleanroom and black out the windows. In this utter darkness, PMTs are monitored for “thermal noise.”

    “At a normal temperature, particles vibrate around inside the PMTs. When this happens, it is possible for electrons to ‘jump off’ and produce a signal that PMTs will detect,” Taylor explained. While most of this “thermal noise” will vanish once the experiment is cooled to liquid xenon temperature (-148 °F), researchers want to ensure the PMT’s dark rate is at the lowest threshold possible before being installed in LZ.

    “Typically, these false signals come from a single photoelectron,” Taylor said. “With the dark test, we can measure how many photoelectrons signals occur every second.”

    How much is too much noise? While a bit of noise (100-1000 events per second) is tolerable; rates closer to 10,000 events per second would be far too high, resulting in too many random signals that could overshadow WIMP signals during the experiment.

    “That’s why it is incredibly important to make sure each PMT has a low dark rate,” said Taylor.

    Lighting it up

    For the second test, called an “after-pulsing” test, researchers will flash a light, imperceptible to the human eye, at the PMTs. This test determines the health of each PMT’s internal vacuum. Why is this important?

    When light from a reaction inside the detector hits a photocathode of a PMT, an electron will be emitted. This single electron will be pulled through the PMT, hitting dynodes. Each time the electron hits an electrode, more electrons are emitted. This process continues, amplifying the original signal, turning the original electron into many, many, many electrons.

    “That’s how we get an electron signal strong enough to read out,” Taylor said. “For that to work, however, those electrons have to be able to bounce between those dynodes without interruption.”

    To decrease particle “traffic,” each PMT has a vacuum. The vacuum ensures there are no gas particles present to interfere with the amplification process. If a vacuum is faulty, gas particles may get in the way and hit an electron. This would cause the gas particle to bounce away and set off a second pulse of electrons, amplifying a signal of its own.

    “This is called an ‘after-pulse,’” Taylor said. “The after-pulse is indicative of how good the vacuum, and thus the PMT, really is.”

    Rather than depriving the PMTs of light as they did during the dark test, researchers now createa signal of their own to measure the after-pulse. To do this, an LED is affixed to the inside of the PALACE.

    “We flash the LED at a rate of 1 kilohertz for 30 seconds. That’s a total of 30,000 flashes of the LED,” Taylor said. While that might sound like a lot of light, it’s actually not even perceptible to the human eye. “Each flash lasts 10 nanoseconds and produces only 50-100 photons—so the human eye can’t detect it.”

    It is enough, however, for the PMT to detect it with a sizable initial pulse. Because researchers know exactly when the initial pulse was created, they can align their data to see when after-pulses occur and measure their strength.

    “This helps us see how healthy the vacuum is and determine if the PMT is fit for LZ,” Taylor said.

    20/20 vision

    After a week of testing, researchers have announced the bottom array has 20/20 vision.

    “Accepting the first of the two PMT arrays onsite, is one of many milestones toward the assembly and installation of the LZ experiment,” said Markus Horn, research support scientist at Sanford Lab and a member of the LZ collaboration. “While the detector assembly progresses at the Surface Lab, underground the installation of the xenon gas and Liquid Nitrogen cooling system begins. That would be the heart and the lung of LZ. But that’s another story!”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
    LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE
    LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA

    CASPAR at SURF


    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”

     
  • richardmitnick 12:43 pm on December 25, 2018 Permalink | Reply
    Tags: A primer on neutrinoless double-beta decay, , , , , , Particles and antiparticles, SURF - Sanford Underground Research Facility, The matter-antimatter conudrum   

    From Sanford Underground Research Facility: “A primer on neutrinoless double-beta decay” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    December 21, 2018
    Erin Broberg

    We asked Vincente Guiseppe about this theorized phenomenon and what it means for our understanding of the universe.

    1
    Vince Guiseppe points to the center of the shield that houses Majorana’s detectors. Credit Matthew Kapust

    At Sanford Underground Research Facility, we often talk about the Majorana Demonstrator’s search for “neutrinoless double-beta decay.”

    U Washington Majorana Demonstrator Experiment at SURF

    We say that this process could be incredibly important to understanding the imbalance of matter and anti-matter in the early universe. We explain how it is difficult to detect, demanding a miniscule background. We show photos of germanium detectors and ultra-pure copper shields, then describe immaculate cleanrooms and show off stylish Tyvek garb.

    But what exactly is neutrinoless double-beta decay?

    To find out, we went directly to the source. Dr. Vincente Guiseppe is the co-spokesperson for the Majorana Demonstrator collaboration and an assistant professor of physics and astronomy at the University of South Carolina.

    The best way to explain this mysterious process, Guiseppe said, is to work backward, defining one word at a time. So, let’s start at the end.

    Decay

    “There are two types of isotopes,” Guiseppe explains, “stable and radioactive.”

    The nuclei of a stable isotope are relaxed, meaning, they have a very low energy state. The nuclei of a radioactive isotope, on the other hand, are in a high energy state—they are very excited. But objects in nature prefer to be relaxed, Guiseppe said.

    So how do nuclei achieve a lower energy state? Through radioactive decay.

    “In nuclear physics, decay means a relaxation or a change of an atomic nucleus,” Guiseppe explained. “Nature allows protons and neutrons to change their makeup to achieve a desirable equilibrium. Once a nucleus is at the lowest energy state, we call it a stable isotope.”

    A lot of times, the words “radioactive decay” sound threatening. That’s because they often are used in the context of radiation you don’twant—radiation that is dangerous or destructive. In reality, though, radioactive decays are taking place all the time.

    “Potassium 40 is an isotope in our bodies,” said Guiseppe. “These isotopes decay 200,000 times per minute.”

    Radioactive decay is simply a nucleus reconfiguring itself through an interplay of matter and energy. Researchers with Majorana are looking for a natural process in which nuclei undergo such a change.

    Double-beta

    Every time an isotope decays, it loses a bit of energy in the form of a particle. Scientists classify types of decays by defining what type of particle comes out of the decay. In the case of beta decay, the particle emitted is an electron, or a beta particle.

    While there are multiple types of decays that could occur within the detector, Majorana researchers are looking specifically for a decay in which a beta particle is emitted.

    “And by ‘double-beta,’ we just mean we are looking for two of these decays simultaneously,” Guiseppe said.

    Neutrino(less)

    All reactions in nature, including beta decays, require symmetry, or a balance. Because of this symmetry, scientists originally assumed that every time an isotope underwent beta decay, it would emit an electron with a uniform energy. The problem was, it didn’t.

    “Electrons emitted from beta decays have a range of energies,” Guiseppe said. “Sometimes it is low, sometimes it is high, but it has this average value that was more or less half of what the scientists thought it should be.”

    This inconsistency lead researchers to realize that there must be another particle emitted—one that could not easily be detected, having no charge and very little mass. That missing particle was a neutrino.

    “When neutrinos were discovered in 1956, their addition to the beta-decay equation was confirmed,” said Guiseppe. “The neutrino balances this fundamental symmetry. With beta decay, there has to be both an electron and a neutrino produced.”

    Hold on a second. By definition, a beta decay must have an electron. By the laws of physics, it must have a neutrino. So why is Majorana looking for neutrinoless double-beta decay?

    “I just spent all this time explaining why you need a neutrino for a beta decay,” Guiseppe said with a smile. “And now, I’m going to say, no, you might not need a neutrino every time.”

    Scientists, Guiseppe said, have good reason to believe that neutrinos have the ability to do something very interesting—the ability to act like anti-neutrinos.

    Neutrinos — the maverick of the early universe

    To better understand the theory, we must first examine what is called the matter and antimatter asymmetry problem.

    According to the Big Bang theory, when the universe first formed, it had equal parts of matter and antimatter. This is a conundrum because, when matter and antimatter meet, they annihilate, leaving a universe filled with pure energy—no planets, stars or comets. And, most certainly, no life.

    So, what happened? Why did matter win out in the cosmic battle? Scientists are seeking an answer to how matter became the dominant form of matter in the universe.

    Many scientists believe there must have been a particle—very much like a neutrino—that acted very inconsistently with our current understanding of the laws of physics. This inconsistency, if detected, could answer the matter and anti-matter asymmetry puzzle. If just one particle acted differently, it could have upset the balance and allowed a remnant of matter to survive.

    For most particles, there exists matter and anti-matter. These types of matter are mirror images of each other—100 percent different. In the early 1930s, however, physicist Ettore Majorana theorized that neutrinos could be their own anti-particle—or what we call today, a Majorana particle.

    3
    Ettore Majorana

    “The claim is that maybe there’s no difference between neutrinos and what we call anti-neutrinos. They may be indistinguishable from each other,” said Guiseppe. “If they have that quality, it could help explain matter and antimatter asymmetry.”

    Neutrinoless double-beta decay — putting it all together

    If neutrinos have this property, it could answer a lot of questions for scientists; for example, how matter became the dominant form of matter in the universe, allowing for the creation of everything we see. But how might Majorana help discover it?

    Researchers are waiting for a double-beta decay to occur inside the Majorana Demonstrator. If it does, and if neutrinos can indeed act like their own antiparticle, then the two neutrinos necessary may interact, possibly being absorbed, making the double-beta decay seem neutrinoless.

    “If two beta decays occur in the Majorana Demonstrator, in close proximity to each other, and neutrinos do have this property, then we will detect the absence of neutrinos,” Guiseppe said.

    Should this rare event be detected, it will require rewriting the Standard Model of Particles and Interactions, our basic understanding of the physical world.

    “What isn’t up for debate,” Guiseppe concluded, “is that if neutrinos are indistinguishable from their anti-particle, then they will allow this neutrinoless double-beta decay process to take place. If they have this property, we will see the decay in Majorana. This is the best type of experiment we have to learn that.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
    LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE
    LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA

    CASPAR at SURF


    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”

     
  • richardmitnick 1:51 pm on December 18, 2018 Permalink | Reply
    Tags: , , SURF - Sanford Underground Research Facility,   

    From Sanford Underground Research Facility: “LZ assembly begins — piecing together a 10-ton detector” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    December 17, 2018
    Erin Broberg

    With main components arriving, researchers have begun the meticulous work of piecing together LUX-ZEPLIN on the 4850 Level.

    1
    Inside the LZ water tank, assembly has begun on the Outer Cryostat Vessel. Photo by Matthew Kapust

    As they peer down into the LUX-ZEPLIN (LZ) water tank from the work deck above, researchers and engineers can finally see the assembly process in full swing. Science and Technology Facilities Council’s Pawel Majewski focuses on the cryostat installation. He recently returned to Sanford Underground Research Facility (Sanford Lab) after nearly half a year away and is thrilled with what he’s seeing.

    2
    The LZ experiment. LZ (LUX-ZEPLIN) will be 30 times larger and 100 times more sensitive than its predecessor, the Large Underground Xenon experiment.

    The race to build the most sensitive direct-detection dark matter experiment got a bit more competitive with the Department of Energy’s approval of a key construction milestone on Feb.9.

    LUX-ZEPLIN (LZ), a next-generation dark matter detector, will replace the Large Underground Xenon (LUX) experiment. The Critical Decision 3 (CD-3) approval puts LZ on track to begin its deep-underground hunt for theoretical particles known as WIMPs in 2020.

    “We got a strong endorsement to move forward quickly and to be the first to complete the next-generation dark matter detector,” said Murdock “Gil” Gilchriese, LZ project director and a physicist at Lawrence Berkeley National Laboratory, the lead lab for the project. The LZ collaboration includes approximately 220 participating scientists and engineers representing 38 institutions around the world.

    The fast-moving schedule allows the U.S. to remain competitive with similar next-generation dark matter experiments planned in Italy and China.

    WIMPs (weakly interacting massive particles) are among the top prospects for explaining dark matter, which has only been observed through its gravitational effects on galaxies and clusters of galaxies. Believed to make up nearly 80 percent of all the matter in the universe, this “missing mass” is considered to be one of the most pressing questions in particle physics.

    LZ will be at least 100 times more sensitive to finding signals from dark matter particles than its predecessor, the Large Underground Xenon experiment (LUX), which was decommissed last year to make way for LZ. The new experiment will use 10 metric tons of ultra-purified liquid xenon, to tease out possible dark matter signals. Xenon, in its gas form, is one of the rarest elements in Earth’s atmosphere.

    “The science is highly compelling, so it’s being pursued by physicists all over the world,” said Carter Hall, the spokesperson for the LZ collaboration and an associate professor of physics at the University of Maryland. “It’s a friendly and healthy competition, with a major discovery possibly at stake.”

    A planned upgrade to the current XENON1T experiment at National Institute for Nuclear Physics’ Gran Sasso Laboratory (the XENONnT experiment) in Italy, and China’s plans to advance the work on PandaX-II, are also slated to be leading-edge underground experiments that will use liquid xenon as the medium to seek out a dark matter signal.

    XENON1T at Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy


    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    PandaX II Dark Matter experiment at Jin-ping Underground Laboratory (CJPL) in Sichuan, China

    Both of these projects are expected to have a similar schedule and scale to LZ, though LZ participants are aiming to achieve a higher sensitivity to dark matter than these other contenders.

    Hall noted that while WIMPs are a primary target for LZ and its competitors, LZ’s explorations into uncharted territory could lead to a variety of surprising discoveries. “People are developing all sorts of models to explain dark matter,” he said. “LZ is optimized to observe a heavy WIMP, but it’s sensitive to some less-conventional scenarios as well. It can also search for other exotic particles and rare processes.”

    LZ is designed so that if a dark matter particle collides with a xenon atom, it will produce a prompt flash of light followed by a second flash of light when the electrons produced in the liquid xenon chamber drift to its top. The light pulses, picked up by a series of about 500 light-amplifying tubes lining the massive tank—over four times more than were installed in LUX—will carry the telltale fingerprint of the particles that created them.

    Daniel Akerib and Thomas Shutt are leading the LZ team at SLAC National Accelerator Laboratory, which includes an effort to purify xenon for LZ by removing krypton, an element that is typically found in trace amounts with xenon after standard refinement processes. “We have already demonstrated the purification required for LZ and are now working on ways to further purify the xenon to extend the science reach of LZ,” Akerib said.

    SLAC and Berkeley Lab collaborators are also developing and testing hand-woven wire grids that draw out electrical signals produced by particle interactions in the liquid xenon tank. Full-size prototypes will be operated later this year at a SLAC test platform. “These tests are important to ensure that the grids don’t produce low-level electrical discharge when operated at high voltage, since the discharge could swamp a faint signal from dark matter,” said Shutt.

    Hugh Lippincott, a Wilson Fellow at Fermi National Accelerator Laboratory (Fermilab) and the physics coordinator for the LZ collaboration, said, “Alongside the effort to get the detector built and taking data as fast as we can, we’re also building up our simulation and data analysis tools so that we can understand what we’ll see when the detector turns on. We want to be ready for physics as soon as the first flash of light appears in the xenon.” Fermilab is responsible for implementing key parts of the critical system that handles, purifies, and cools the xenon.

    All of the components for LZ are painstakingly measured for naturally occurring radiation levels to account for possible false signals coming from the components themselves. A dust-filtering cleanroom is being prepared for LZ’s assembly and a radon-reduction building is under construction at the South Dakota site—radon is a naturally occurring radioactive gas that could interfere with dark matter detection. These steps are necessary to remove background signals as much as possible.

    The vessels that will surround the liquid xenon, which are the responsibility of the U.K. participants of the collaboration, are now being assembled in Italy. They will be built with the world’s most ultra-pure titanium to further reduce background noise.

    To ensure unwanted particles are not misread as dark matter signals, LZ’s liquid xenon chamber will be surrounded by another liquid-filled tank and a separate array of photomultiplier tubes that can measure other particles and largely veto false signals. Brookhaven National Laboratory is handling the production of another very pure liquid, known as a scintillator fluid, that will go into this tank

    The cleanrooms will be in place by June, Gilchriese said, and preparation of the cavern where LZ will be housed is underway at SURF. Onsite assembly and installation will begin in 2018, he added, and all of the xenon needed for the project has either already been delivered or is under contract. Xenon gas, which is costly to produce, is used in lighting, medical imaging and anesthesia, space-vehicle propulsion systems, and the electronics industry.

    “South Dakota is proud to host the LZ experiment at SURF and to contribute 80 percent of the xenon for LZ,” said Mike Headley, executive director of the South Dakota Science and Technology Authority (SDSTA) that oversees SURF. “Our facility work is underway and we’re on track to support LZ’s timeline.”

    UK scientists, who make up about one-quarter of the LZ collaboration, are contributing hardware for most subsystems. Henrique Araújo, from Imperial College London, said, “We are looking forward to seeing everything come together after a long period of design and planning.

    Kelly Hanzel, LZ project manager and a Berkeley Lab mechanical engineer, added, “We have an excellent collaboration and team of engineers who are dedicated to the science and success of the project.” The latest approval milestone, she said, “is probably the most significant step so far,” as it provides for the purchase of most of the major components in LZ’s supporting systems.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
    LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE
    LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA

    CASPAR at SURF


    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”

     
  • richardmitnick 1:45 pm on December 17, 2018 Permalink | Reply
    Tags: , , , Lux Zeplin project, PMT's-photomultiplier tubes, SURF - Sanford Underground Research Facility,   

    From Brown University: “Massive new dark matter detector gets its ‘eyes’” 

    Brown University
    From Brown University

    1
    The detector’s “eyes”
    Powerful light sensors assembled at Brown into two large arrays will keep watch on the LUX-ZEPLIN dark matter detector, looking for the tell-tale flashes of light that indicate interaction of a dark matter particle inside the detector. Credit: Nick Dentamaro

    LBNL Lux Zeplin project at SURF

    December 17, 2018
    Kevin Stacey

    Brown University researchers have assembled two massive arrays of photomultiplier tubes, powerful light sensors that will serve as the “eyes” for the LUX-ZEPLIN dark matter detector, which will start its search for dark matter particles in 2020.

    The LUX-ZEPLIN (LZ) dark matter detector, which will soon start its search for the elusive particles thought to account for a majority of matter in the universe, had the first of its “eyes” delivered late last week.

    The first of two large arrays of photomultiplier tubes (PMTs) — powerful light sensors that can detect the faintest of flashes — arrived last Thursday at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, where LZ is scheduled to begin its dark matter search in 2020. The second array will arrive in January. When the detector is completed and switched on, the PMT arrays will keep careful watch on LZ’s 10-ton tank of liquid xenon, looking for the telltale twin flashes of light produced if a dark matter particle bumps into a xenon atom inside the tank.

    The two arrays, each about 5 feet in diameter and holding a total of 494 PMTs, were shipped to South Dakota via truck from Providence, Rhode Island, where a team of researchers and technicians from Brown University spent the past six months painstakingly assembling them.

    “The delivery of these arrays is the pinnacle of an enormous assembly effort that we’ve executed here in our cleanroom at the Brown Department of Physics,” said Rick Gaitskell, a professor of physics at Brown University who oversaw the construction of the arrays. “For the last two years, we’ve been making sure that every piece that’s going into the devices is working as expected. Only by doing that can we be confident that everything will perform the way we want when the detector is switched on.”

    The Brown team has worked with researchers and engineers from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and from Imperial College London to design, procure, test, and assemble all of the components of the array. Testing of the PMTs, which are manufactured by the Hamamatsu Corporation in Japan, was performed at Brown and at Imperial College “The PMTs have already qualified for significant air miles, even before they started their 2,000-mile journey by road from Rhode Island to South Dakota,” Gaitskell said.

    “The PMTs have already qualified for significant air miles, even before they started their 2,000-mile journey by road from Rhode Island to South Dakota,” Gaitskell said.

    Catching a WIMP

    Nobody knows exactly what dark matter is. Scientists can see the effects of its gravity in the rotation of galaxies and in the way light bends as it travels across the universe, but no one has directly detected a dark matter particle. The leading theoretical candidate for a dark matter particle is the WIMP, or weakly interacting massive particle. WIMPs can’t be seen because they don’t absorb, emit or reflect light. And they interact with normal matter only on very rare occasions, which is why they’re so hard to detect even when millions of them may be traveling through the Earth and everything on it each second.

    The LZ experiment, a collaboration of more than 250 scientists worldwide, aims to capture one of those fleetingly rare WIMP interactions, and thereby characterize the particles thought to make up more than 80 percent of the matter in the universe. The detector will be the most sensitive ever built, 50 times more sensitive than the LUX detector, which wrapped up its dark matter search at SURF in 2016.

    3
    This rendering shows a cutaway view of the LZ xenon tank (center), with PMT arrays at the top and bottom of the tank. (Credit: Greg Stewart/SLAC National Accelerator Laboratory)

    The PMT arrays are a critical part of the experiment. Each PMT is a six-inch-long cylinder that is roughly the diameter of a soda can. To form arrays large enough to monitor the entire LZ xenon target, hundreds of PMTs are assembled together within a circular titanium matrix. The array that will sit on top of the xenon target has 253 PMTs, while the lower array has 241.

    PMTs are designed to amplify weak light signals. When individual photons (particles of light) enter a PMT, they strike a photocathode. If the photon has sufficient energy, it causes the photocathode to eject one or more electrons. Those electrons strike then an electrode, which ejects more electrons. By cascading through a series of electrodes the original signal is amplified by over a factor of a million to create a detectable signal.

    LZ’s PMT arrays will need every bit of that sensitivity to catch the flashes associated with a WIMP interaction.

    “We could be looking for events emitting as few as 20 photons in a huge tank containing 10 tons of xenon, which is something that the human visual system wouldn’t be able to do,” Gaitskell said. “But it’s something these arrays can do, and we’ll need them to do it in order to see the signal from rare particle events.”

    The photons are produced by what’s known as a nuclear recoil event, which produces two distinct flashes. The first comes at the moment a WIMP bumps into a xenon nucleus. The second, which comes a few hundred microseconds afterward, is produced by the ricochet of the xenon atom that was struck. It bounces into the atoms surrounding it, which knocks a few electrons free. The electrons are then drifted by an electric field to the top of the tank, where they reach a thin layer of xenon gas that converts them into light.

    In order for those tiny flashes to be distinguishable from unwanted background events, the detector needs to be protected from cosmic rays and other kinds of radiation, which also cause liquid xenon to light up. That’s why the experiment takes place underground at SURF, a former gold mine, where the detector will be shielded by about a mile of rock to limit interference.

    A clean start

    The need to limit interference is also the reason that the Brown University team was obsessed with cleanliness while they assembled the arrays. The team’s main enemy was plain old dust.

    “When you’re dealing with an instrument that’s as sensitive as LZ, suddenly things you wouldn’t normally care about become very serious,” said Casey Rhyne, a Brown graduate student who had a leading role in building the arrays. “One of the biggest challenges we had to confront was minimizing ambient dust levels during assembly.”

    Each dust particle carries a minuscule amount of radioactive uranium and thorium decay products. The radiation is vanishingly small and poses no threat to people, but too many of those specks inside the LZ detector could be enough to interfere with a WIMP signal.

    4
    Much of the assembly work was done while the arrays sat inside PALACE, an ultraclean enclosure designed to keep the arrays dust-free. Nick Detamaro

    In fact, the dust budget for the LZ experiment calls for no more than one gram of dust in the entire 10-ton instrument. Because of all their nooks and crannies, the PMT arrays could be significant dust contributors if pains were not taken to keep them clean throughout construction.

    The Brown team performed most of its work in a “class 1,000” cleanroom, which allows no more than 1,000 microscopic dust particles per cubic foot of space. And within that cleanroom was an even more pristine space that the team dubbed “PALACE (PMT Array Lifting And Commissioning Enclosure).” PALACE was essentially an ultraclean exoskeleton where much of the actual array assembly took place. PALACE was a “class 10” space — no more than 10 dust particles bigger than one hundredth the width of a human hair per cubic foot.

    But the radiation concerns didn’t stop at dust. Before assembly of the arrays began, the team prescreened every part of every PMT tube to assess radiation levels.

    “We had Hamamatsu send us all of the materials that they were going to use for the PMT construction, and we put them in an underground germanium detector,” said Samuel Chan, a graduate student and PMT system team leader. “This detector is very good at detecting the radiation that the construction materials are emitting. If the intrinsic radiation levels were low enough in these materials, then we told Hamamatsu to go ahead and use them in the manufacture of these PMTs.”

    7
    A PMT is carefully inserted into the array inside PALACE. Nick Dentamaro

    The team is hopeful that all the work contributed over the past six months will pay dividends when LZ starts its WIMP search.

    “Getting everything right now will have a huge impact less than two years from now when we switch on the completed detector and we’re taking data,” Gaitskell said. “We’ll be able to see directly from that data how good of a job we and other people have done.”

    Given the major increase in dark matter search sensitivity that the LUX-ZEPLIN detector can deliver compared to previous experiments, the team hopes that this detector will finally identify and characterize the vast sea of stuff that surrounds us all. So far, the dark stuff has remained maddeningly elusive.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
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