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  • 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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    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: , , , , 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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    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.

     
  • richardmitnick 12:53 pm on November 20, 2018 Permalink | Reply
    Tags: “Nuclear astrophysics is about what goes on inside the star not outside of it”, , SURF - Sanford Underground Research Facility,   

    From Notre Dame University: “Unearthing the Secrets of a Star” 

    Notre Dame bloc

    From University of Notre Dame

    The Goal

    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).


    SURF Above Ground

    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.”

    ______________________________________
    “The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”
    ______________________________________

    SURF is located in the former Homestake Gold Mine, which operated for more than a century extracting ore from hundreds of miles of tunnels, thousands of feet below the earth’s surface. That depth is key to projects like CASPAR. With a keen sense of the irony at play, Robertson explains that researchers must “reproduce the stellar environment” by getting as far away from that environment as possible to reduce the cosmic radiation that constantly bombards the earth and creates “noise” which interferes with sensitive physics experiments.

    “When we go underground, there’s a lot of rock above us that’s a mild shielding from cosmic rays,” Robertson said. “Once you get underground, cosmic ray background almost completely disappears.”

    It’s a fairly direct rationale for a project that took a winding path to fruition.

    Finding a Site

    Notre Dame’s involvement with SURF has its origins in a facility called the Deep Underground Science and Engineering Laboratory (DUSEL), planned by the National Science Foundation (NSF) as a complex of laboratories for research in multiple fields: biology, chemistry, geology, as well as physics.

    Notre Dame researchers were especially interested in one aspect of the DUSEL concept called DIANA (Dual Ion Accelerators for Nuclear Astrophysics). And with good reason, according to Robert J. Bernhard, the University’s vice president for research. “The nuclear astrophysics community identified DIANA as a priority, and identified Michael Wiescher to lead that facility,” Bernhard said.

    Wiescher, the Freimann Professor of Nuclear Physics at Notre Dame, led the planning for the DIANA portion of the NSF proposal. That is, right up until sequestration of federal spending made funding of the project impossible. The NSF would eventually ask Wiescher and Notre Dame to withdraw the DIANA proposal, with hopes of one day revisiting it.

    “So the question was, do we just drop it, or do we move ahead?” Wiescher recalls. “And we decided to move ahead, with a smaller scale version.”

    Moving ahead with a smaller project allowed the NSF to still be involved, while a coalition of other partners was formed, including the South Dakota School of Mines and Technology, and Colorado School of Mines. The collaborative nature of CASPAR is indicative of a trend in scientific research at large, and especially at Notre Dame, according to Bernhard. For its part, Notre Dame is strategically investing in labs and equipment that serve multiple researchers and collaborative programs.

    ”Instead of buying equipment for individual labs, we’re directing funding in high performance, shared facilities such as the integrated imaging facility, the center for nano research and technology, the genomics and bioinformatics facility, the mass spectrometry and proteomics facility,” Bernhard said.

    That same philosophy is at work at SURF, which, like CASPAR, has its own indirect path to realization. The Homestake Mine was founded after an expedition led by George Armstrong Custer discovered gold in South Dakota’s Black Hills in 1874. Five years later, the Homestake Mining Company began operations, eventually carving out 370 miles of tunnels as deep as 8,000 feet, creating one of the deepest mines in the country. The gold vein was eventually exhausted after producing 1.25 million kilograms of gold in its lifetime (roughly $80 billion at today’s rates), and Homestake shut down in 2001.

    The closing of Homestake resulted in an economic and identity crisis for Lead and the surrounding area. However, in addition to its gold mining past, Homestake had a unique astrophysics connection.

    2
    The Compact Accelerator System is modular, to allow for transport down the mine shaft.

    In 1965, Ray Davis, a nuclear chemist from Brookhaven National Laboratory, began building an experiment deep in the Homestake mine with the goal of counting neutrinos, subatomic particles produced in fusion reactions inside stars. In 2002, Davis was awarded a share of the Nobel Prize for Physics for his neutrino work at Homestake.

    When Homestake announced it would close the mine, physicists, aware of Davis’ neutrino success, proposed converting it into a deep underground laboratory. In 2004, the South Dakota Legislature created the South Dakota Science and Technology Authority (SDSTA) to work with the scientists proposing the lab. In 2006, Homestake Mining Co. donated the underground mine to the SDSTA. Also in 2006, the SDSTA accepted a $70 million gift from South Dakota philanthropist T. Denny Sanford, who stipulated that $20 million of the donation be used for a Sanford Science Education Center.

    Then the real work began, according to Ani Aprahamian, Notre Dame’s Freimann Professor of Experimental Nuclear Physics and a member of SDSTA’s board.

    “When you have a mine, it’s just people going under to dig at the rock. It’s dirty, filthy,” Aprahamian said. “This is a laboratory that requires a high level of cleanliness, underground. It’s a little bit more than just building a scientific lab, like you would above ground. So the transformation was quite astounding.”

    The first step in that transformation was to pump millions of gallons of water out of the tunnels of the old mine. That task took months. Then came the installation of the power and technology infrastructure required in the roughly 4,400 square feet occupied by CASPAR. Meanwhile, the group of Notre Dame astrophysicists had to devise a way to disassemble and move an accelerator that had been on campus for 10 years to its new underground home.

    “We worked in conjunction with the team at SURF so that everything we designed and built at Notre Dame was modular,” said Robertson. “The idea was that we could dismantle every section and bring it down in much smaller pieces and rebuild it from scratch. We packed it all up into two U-Haul vans and dragged it all the way from campus to SURF.”

    When it arrived, the equipment was brought down the mine shaft via infrastructure originally designed to move men and minerals, not highly sensitive scientific equipment. Robertson recalls the series of roughly two-mile trips from the surface to the underground lab taking upwards of 45 minutes because of the pace at which the conveyances had to travel with accelerator parts on board.

    The Unique Journey to a Unique Lab

    It’s just one of the ways the space’s mining past is meeting its scientific present. Indeed, a visit to CASPAR is unlike a visit to any other laboratory environment. It starts with a comprehensive safety briefing and signing of a series of waivers. Before descending into the mine, one dons overalls, steel-tipped boots, safety goggles and a hard hat and attaches a carbon monoxide detector around the waist. Next, you pick up a gold medallion with a number inscribed on it and enter your name and number on a clipboard. If the medallion is missing at the end of the day, it becomes clear that someone is still underground in the mine. While certainly effective, it’s a fascinating juxtaposition in the highly technical work of exploring the origins of the universe.

    The descent into the mine takes place in a cage that, at most, holds 15 people. The approximately mile-long trip takes 10 minutes without lab equipment, which requires a slower pace and more time. Yet even those 10 minutes can seem longer. The only light in the cage is from a headlamp on the cage operator’s hard hat, which briefly illuminates the wood supports and rock pilings framing the shaft.

    After the descent, you arrive at what is familiarly called the 4850 Level of SURF. You exit into a surprisingly well-lit area with tunnels, or “drifts” in mining parlance, running right and left. CASPAR is located through the left, mile-long tunnel. It’s a startling experience to emerge through the dark tunnel and enter the pristine, high-tech environs of CASPAR. There, Notre Dame researchers and doctoral students have nearly completed reassembly of the accelerator that was shipped in parts from Notre Dame, like an incredibly complex jigsaw puzzle. Experiments are expected to begin in the summer of 2016.

    The groundbreaking scientific breakthroughs the CASPAR researchers are seeking cannot be achieved without the invaluable technical expertise of the former Homestake miners, who were brought back to operate and maintain the mine equipment still being used. The miners and astrophysicists have formed a close working relationship, and Wiescher indicates there is a bond between the two groups that extends beyond just the common workspace.

    “Our goal in CASPAR is to measure the evolution of the elements in the stars,” he said. “There are a number of questions that need to be answered, one being the ratio of carbon to oxygen in our universe. That will be determined by one of the reactions we want to measure. But also, we want to understand the buildup of heavy elements. When you look at old stars – those that came to be around the time of the Big Bang – there are very few elements. You can see in younger stars the elements slowly build up, including heavy elements, such as gold.”

    In other words, Notre Dame researchers are using a retired gold mine in a town called Lead, to determine what reactions lead to the formation of gold in stars, among other things.

    CASPAR is on schedule to be the first such project of its kind to yield results. When it does, Wiescher said the knowledge will have implications across multiple fields of study, most obvious astronomy and the material sciences. Robertson adds that sometimes these kinds of experiments yield other technologies that have broad public familiarity. Nuclear physics experiments have been instrumental in developing MRI and PET scans, for example. While those kinds of outcomes are not an intended goal of projects like CASPAR, Bernhard believes in today’s world they’re nonetheless critical.

    CASPAR at SURF

    3
    Studying the stars from underground

    7
    CASPAR accelerator at SURF

    CASPAR experiment target at SURF

    “Nationally, there is an increasing expectation that universities will be a vehicle of discovery that will continue to provide the basic foundation that will drive better understanding of our world and our future economy,” Bernhard said. “The CASPAR project is an excellent example of this type of research.”

    For now, the precious gold researchers seek is a deeper understanding of our universe. It happens that the best way to do so is to build a deeper lab, where the cosmos can be shut out in hopes of revealing its secrets.

    Produced by the Office of Public Affairs and Communications

    Writers
    Andy Fuller and Bill Gilroy
    Designer
    Nevin McElwrath
    Developer
    Shawn Maust
    Photographer
    Barbara Johnston
    Videographer
    Ryan Blaske
    Illustrator
    Justin Zimmerman

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Notre Dame Campus

    The University of Notre Dame du Lac (or simply Notre Dame /ˌnoʊtərˈdeɪm/ NOH-tər-DAYM) is a Catholic research university located near South Bend, Indiana, in the United States. In French, Notre Dame du Lac means “Our Lady of the Lake” and refers to the university’s patron saint, the Virgin Mary.

    The school was founded by Father Edward Sorin, CSC, who was also its first president. Today, many Holy Cross priests continue to work for the university, including as its president. It was established as an all-male institution on November 26, 1842, on land donated by the Bishop of Vincennes. The university first enrolled women undergraduates in 1972. As of 2013 about 48 percent of the student body was female.[6] Notre Dame’s Catholic character is reflected in its explicit commitment to the Catholic faith, numerous ministries funded by the school, and the architecture around campus. The university is consistently ranked one of the top universities in the United States and as a major global university.

    The university today is organized into five colleges and one professional school, and its graduate program has 15 master’s and 26 doctoral degree programs.[7][8] Over 80% of the university’s 8,000 undergraduates live on campus in one of 29 single-sex residence halls, each of which fields teams for more than a dozen intramural sports, and the university counts approximately 120,000 alumni.[9]

    The university is globally recognized for its Notre Dame School of Architecture, a faculty that teaches (pre-modernist) traditional and classical architecture and urban planning (e.g. following the principles of New Urbanism and New Classical Architecture).[10] It also awards the renowned annual Driehaus Architecture Prize.

     
  • richardmitnick 11:20 am on November 20, 2018 Permalink | Reply
    Tags: , Nuclides and Isotopes, SURF - Sanford Underground Research Facility   

    From Sanford Underground Research Facility: “A ‘game board’ for astrophysicists” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    November 19, 2018
    Erin Broberg

    A nuclides chart is designed to help researchers study the nucleosynthesis of elements—or how they are created.

    1
    Matthew Kapust

    Just outside a thick lead door leading to the Compact Accelerator System for Performing Astrophysical Research (CASPAR) in the experiment’s control room, hangs a massive chart. Hundreds of small, colorful blocks identify some of the universe’s smallest units in three vibrant bands that streak across the chart. It is as if an artist took a brush and swiped it across the page. But it isn’t a painting; it’s the chart of nuclides.

    “The periodic table is a chart of atoms, but this is a chart of just the nuclei of those atoms—the stable and unstable isotopes of those atoms,” said Mark Hanhardt, support scientist for Sanford Underground Research Facility (Sanford Lab). “Here, we don’t take into account the electrons at all—just the nucleus.” Hanhardt, a Ph.D. candidate in physics at the South Dakota School of Mines and Technology (SD Mines), is focusing on CASPAR.

    While the periodic table allows scientists to understand the chemical properties of elements, this chart is specifically designed to help researchers study the nucleosynthesis of elements—or how they are created.

    What happens to a nucleus if a neutron is added? If a beta decay occurs? Scientists can locate an element’s nuclei on the chart and visualize the changes that occur at a nuclear level. The numerous details contained in this chart are a bit dizzying. To explain just how this powerful tool is used, Hanhardt has developed a simple analogy.

    “If you add a proton, you move one square up. If you add a neutron, you move one over to the right,” said Hanhardt. “Truly, the chart of nuclides is CASPAR’s game board.”

    The CASPAR collaboration will use a low-energy accelerator to study the creation of elements inside the heart of stars; using this “game board” helps them explore and track the evolution of elements over time.

    The Game Board

    This game board has some three very important rules:

    Rule 1: Start at the beginning.

    The Big Bang created two elements—hydrogen and helium.

    “That is where the elements start,” said Frank Strieder, associate professor of physics at SD Mines and principal investigator for CASPAR. “Over time, they build upon each other, moving their way up the board.”

    Rule 2: Level up.

    From hydrogen and helium, there are multiple ways to “level up” to a heavier element.

    The first is through nuclear fusion, which pushes two elements together, creating a heavier element. Other processes include the slow capture of individual neutrons (called the s-Process), the collision of two stars (called the r-Process) or the beta decay of a neutron.

    Rule 3: Follow the Valley of Stability.

    Isotopes with equal numbers of protons and neutrons are usually more stable than those isotopes with very different numbers. Should a nucleus gain too many of any one particle, it becomes unstable. The thick bands streaking across the chart of nuclides represent what Hanhardt has dubbed the “Valley of Stability.”

    “In this band, the isotopes have a relatively equal number of protons and neutrons in each nucleus, so they tend to be more stable,” said Hanhardt. “As isotopes gain too many protons or neutrons, however, they begin to stray from the main path, further from the Valley of Stability, and the more likely it is that a beta decay will occur.”

    Playing with the s-process

    The rules help researchers better understand how elements can evolve over time. The CASPAR collaboration is most interested in what is called the Slow Neutron Capture Process, or the s-Process. The s-process accounts for the creation of half of all elements heavier than iron.

    “Without the s-process, the universe would be very boring, and it probably would not have complex life,” said Strieder.

    Here’s how the s-process works, according to Hanhardt.

    “Say you start with an element like iron-58. If there is a neutron available, just a free neutron floating around, the iron nucleus can capture it, creating iron-59, another isotope of iron. If that isotope would be stable, it would stick around; however, it is unstable and will undergo beta decay. Beta decay means a neutron is changed into a proton. This will move the nucleus up one and over one to the left on the chart, making it a new element.”

    Through this very slow process, you take a jagged path up the chart, building many of the heavier elements. In order for this process to happen, though, there must be a free neutron available. That’s a bit more difficult that it sounds.

    “Free neutrons only exist on their own for 10-15 minutes before they decay,” Strieder said. “So, in order to create these elements, there has to be a place in the universe where you have neutrons being created, nuclei that are ready to capture a neutron and a temperature just perfect for these reactions to take place.”

    Scientists have a pretty good idea where this happens: in multi-layered stars called thermally pulsing asymptotic giant branch stars (TP-AGB). An example of such a star is “Mira” in the constellation Cetus. What they don’t know, however, is the rate and energy at which the neutrons are produced and captured.

    Two upcoming CASPAR experiments aim to discover just how quickly those neutrons are created and how they join other elements over time.

    3
    New ultraviolet images from NASA’s Galaxy Evolution Explorer show a speeding star that is leaving an enormous trail of “seeds” for new solar systems. The star, named Mira (pronounced my-rah) after the latin word for “wonderful,” is shedding material that will be recycled into new stars, planets and possibly even life as it hurls through our galaxy.

    Defining the Rules

    To study these rates, researchers at CASPAR hope to duplicate the reactions they know occur in TP-AGB stars, creating free neutrons. They will be the first people on earth to study these reactions at a low energy—an energy that is the same in the heart of the star.

    “The astrophysicists take these numbers we discover and put it into their model of how a star works,” said Strieder. “With this, we can determine how much of the heavier elements were produced per star. Then we can calculate the number of heavier elements that were produced in the entire universe, and check if that is consistent with the number of elements we measure on earth.”

    These are big questions to ask of such little reactions. However, it is a fundamental piece in the universal puzzle.

    “If we go back to the game board analogy,” said Hanhardt, “we are not so much looking at one specific move on the board, but rather investigating the rules of the game itself. The really fundamental rules—where do these neutrons come from and how fast do they come?”

    Bechtel Chart of the Nuclides

    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 10:43 am on November 14, 2018 Permalink | Reply
    Tags: , , , , SURF - Sanford Underground Research Facility, The search for Dark Matter, ,   

    From Sanford Underground Research Facility: “Success of experiment requires testing” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    November 13, 2018
    Erin Broberg

    1
    Tomasz Biesiadzinski, project scientist for SLAC National Accelerator Laboratory (SLAC), works on the mock PMT [photomultiplier tubes] array. Erin Broberg

    “The LZ detector is kind of like a spacecraft,” said Tomasz Biesiadzinski, project scientist for SLAC National Accelerator Laboratory (SLAC). “Repairing it after it’s installed would be very difficult, so we do everything we can to make sure it works correctly the first time.”

    LZ Dark Matter Experiment at SURF lab

    LBNL LZ project at SURF, Lead, SD, USA

    Biesiadzinski himself is responsible for planning and carrying out tests during the assembly of time projection chamber (TPC), the main detector for LUX-ZEPLIN experiment (LZ). Currently being constructed on the 4850 Level at Sanford Underground Research Facility (Sanford Lab), this main detector consists of a large tank that will hold 7 tonnes of ultra-pure, cryogenic liquid xenon maintained at -100o C. All the pieces of this detector are designed to function with precision; it’s Biesiadzinski job to verify that each part continues to work correctly as they are integrated. That includes hundreds of photomultiplier tubes (PMT).

    Test run

    The most recent test was piecing together an intricate mock array for the PMTs, which will detect light signals created by the collision of a dark matter particle and a xenon atom, inside the main detector. In a soft-wall cleanroom in the Surface Laboratory at Sanford Lab, Biesiadzinski and his team carefully practiced placing instruments like thermometers, sensors and reflective covering. They practiced installing routing cabling, including PMT high voltage power cables, PMT signal cables and thermometer cables.

    “Essentially, we wanted to gain experience so we could be faster during the actual assembly. The faster we work, the more we limit dust exposure and therefore potential backgrounds,” said Biesiadzinski. “It was also an opportunity to test fit real components. We did find that there were some very tight places that motivated us to slightly redesign some small parts to make assembly easier.”

    These tests will make the installment of the actual LZ arrays much smoother.

    “LZ’s main detector will have two PMT arrays, one on the top of the tank and one on the bottom,” Biesiadzinski explained. “The bottom array will hold 241 PMTs pointing up into the liquid Xenon volume of the main detector. The top array will hold PMTs 253 pointing down on the liquid Xenon and the gas layer above it in the main detector.”

    In total, there will be 494 PMTs lining the main detector. If a WIMP streaks through the tank and strikes a xenon nucleus, two things will happen. First, the xenon will emit a flash of light. Then, it will release electrons, which drift in an electric field to the top of the tank, where they will produce a second flash of light. Hundreds of PMTs will be waiting to detect a characteristic combination of flashes from inside the tank—a WIMPs’ telltale signature.

    “Both arrays—top and bottom—record the light from particle interactions inside the detector, including, hopefully, dark matter,” said Biesiadzinski. “This data allows us to estimate both the energy created and 3D location of the interaction.”

    Catching light

    The PMTs used for LZ are extremely sensitive. Not only can they distinguish individual photons of light arriving just a few tens of nanoseconds apart, they can also see the UV light produced by xenon that is far outside the human vision range. The X-Y location of events in the detector can be measured using the top PMT array to within a few millimeters for sufficiently energetic events.

    To insure every bit of light makes its way to a PMT, the inside surfaces of the arrays are covered with Polytetrafluoroethylene (PTFE or teflon), a material highly reflective to xenon scintillation light, in between the PMT faces.

    “This way, photons that don’t enter the PMTs right away—and are therefore not recorded—are reflected and will get a second, third, and so on, chance of being detected as they bounce around the detector,” said Biesiadzinski.

    Researchers will also cover the outside of the bottom array, including all of the cables, with PTFE to maximize light collection there. Light recorded there by additional PMTs that are not part of the array, allow us to measure radioactive backgrounds that can contaminate the main detector.

    Keeping it “clean”

    In addition to being very specific, these PMTs are also ultra-clean.

    “By clean, we mean radio-pure,” said Briana Mount, director of the BHUC, where 338 of LZ’s PMTs have already been tested for radio-purity.

    The tiniest amounts of radioactive elements in the very materials used to construct LZ can also overwhelm the rare-event signal. Radioactive elements can be found in rocks, titanium—even human sweat. As these elements decay, they emit signals that quickly light up ultra-sensitive detectors. To lessen these misleading signatures, researchers assay, or test, their materials for radio-purity using low-background counters (LBCs).

    “Our PMTs are special made to have very low radioactivity so as to not overwhelm a very sensitive detector like LZ with background signal,” said Biesiadzinski.

    Testing the PMTs at the BHUC allows researchers to understand exactly how much of a remaining background they can expect to see from these materials during the experiment. Mount explained that most of the samples currently being assayed at the BHUC are LZ samples, including cable ties, wires, nuts and bolts.

    “We have assayed every component that will make up LZ,” said Kevin Lesko, senior physicist at Lawrence Berkeley National Lab (Berkeley Lab) and a spokesperson for LZ. “At this point we have performed over 1300 assays with another 800 assays planned. These have kept BHUC and the UK’s Boulby LBCs fully occupied for approximately 4 years. These assays permit us ensure no component contributes a major background to the detector and also allows us to assemble a model of the backgrounds for the entire detector before we turn on a single PMT.”

    For a visual description and breakdown of LZ’s design, watch this video created by SLAC.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    But most of the real work was done by Vera Rubin a Woman in STEM

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    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

     
  • richardmitnick 10:23 pm on October 30, 2018 Permalink | Reply
    Tags: , , , SURF - Sanford Underground Research Facility,   

    From Sanford Underground Research Facility: “Five years later, the hunt continues” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    October 29, 2018
    Erin Broberg

    Second-generation dark matter detector prepares to continue the search for WIMPs.

    1
    The LZ cryostat undergoes leak tests in the Surface Lab cleanroom. Matthew Kapust

    Five years ago, lead scientists for the Large Underground Xenon (LUX) experiment presented the first scientific results to come from the 4850 Level of Sanford Lab since Ray Davis’ Nobel-winning research in the 1960s. And the results were big.

    After a run of just over three months operating a mile underground, LUX had proven itself the most sensitive dark matter detector in the world.

    “LUX is blazing the path to illuminate the nature of dark matter,” said Brown University physicist Rick Gaitskell, co-spokesperson for LUX with physicist Dan McKinsey of Yale University, at the time.

    Dark matter, so far observed only by its gravitational effects on galaxies and clusters of galaxies, is the predominant form of matter in the universe—making up more than 80 percent of all matter.

    Women in STEM – Vera Rubin
    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster

    Coma cluster via NASA/ESA Hubble

    But most of the real work was done by Vera Rubin

    Fritz Zwicky from http:// palomarskies.blogspot.com


    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    Weakly interacting massive particles, or WIMPs—so-called because they rarely interact with ordinary matter except through gravity—are the leading theoretical candidates for dark matter. The mass of WIMPs is unknown, but theories and results from other experiments suggest a number of possibilities.

    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.

    U Washington Large Underground Xenon at SURF, Lead, SD, USA


    U Washington Lux Dark Matter 2 at SURF, Lead, SD, USA

    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.

    LBNL LZ project at SURF, Lead, SD, USA


    LZ Dark Matter Experiment at SURF lab

    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.”

    This month, we celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment. The following are just a few of the steps being taken by the LZ collaboration to make an experiment 30 times bigger and 100 times more sensitive—all in the pursuit of WIMPs.

    Renovating the Davis Cavern

    To make room for this scaled-up experiment, renovations had to occur inside the Davis Cavern.

    “Planning for this renovation started several years ago—even before LUX was built,” said John Keefner, underground operations engineer. “We had to refit the cavern and existing infrastructure to allow for the installation of LZ.”

    The Davis Cavern renovation project included removing an existing cleanroom, tearing down a wall between two former low-background counting rooms, installing a new hoist system, building a work deck and preparing the water tank itself to accommodate the larger cryostat.

    Reducing radon

    In addition to hosting the experiment nearly a mile underground to escape cosmic radiation, additional protections had to be put in place, including a radon-reduction system that was installed to further ensure the experiment remains free of backgrounds that could interfere with the results.

    Radon, a naturally occurring radioactive gas, significantly increases background noise in sensitive physics projects. The radon reduction system pressurizes, dehumidifies and cools air to minus 60 degrees Celsius before sending it through two columns, each filled with 1600 kg of activated charcoal, which remove the radon. The pressure is released, warmed and humidified before flowing into the cleanroom.

    “Our detectors need very low levels of radon,” said Dr. Richard Schnee, who is head of the physics department at SD Mines and a collaborator with LZ. Schnee heads up the SD Mines team that designed a radon reduction system that will be used underground. While the radon levels at the 4850 Level are safe for humans, they are too high for sensitive experiments like LZ, which go deep underground to escape cosmic radiation, Schnee explained. “We will take regular air from the facility and the systems will reduce the levels by 1,000 times or more.”

    Cryostat

    The arrival of the LZ cryostats at Sanford Lab in May 2018 marked a significant milestone in the LZ project, as the cryostat was several years in the making and is a key component in the experiment.

    The cryostat works in a similar way to a big thermos flask and keeps the detector at freezing temperatures. This is crucial because the detector uses xenon, which at room temperature is a gas. For the experiment to work, the xenon must be kept in a liquid state, which is only achievable at about minus 148 degrees Fahrenheit.

    After being delivered to the surface facility at Sanford Lab, the outer cryostat vessel of the cryostat chamber spent five weeks being fully assembled and leak-checked in the Assembly Lab clean room. It has now been disassembled and packaged for transportation from the surface to the underground location on the 4850 Level. The inner cryostat vessel also passed its leak test.

    Water tank passivation

    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.

    “The LUX water tank needed a number of ports added or modified to support the LZ infrastructure. We also added the capability to install small hoisting equipment on the ceiling of the tank,” said Simon Fiorucci, a physicist with Lawrence Berkeley National Laboratory, who oversaw LUX operations at Sanford Lab and will serve in a similar role for LZ.

    Once these steps were completed, the entire inside of the tank had to be re-passivated to prevent rusting during its many years of service ahead. Finally, the tank was filled to the brim and monitored for a week to ensure there were no leaks.

    Acrylic tanks

    Additionally, LZ will include a component not present in LUX—nine acrylic tanks, filled with a liquid scintillator, will form a veto system around the experiment, allowing researchers to better recognize a WIMP if they see one.

    The acrylic tanks, or more precisely the liquid scintillator inside the tanks, are crucial in bringing the experiment to a new level of sensitivity—100 times greater than LUX—by identifying neutrons, which can mimic dark matter signals.

    “Recent dark matter searches have found that neutrons can be a pernicious background,” said Carter Hall, former LZ spokesperson and professor of physics at the University of Maryland. “The acrylic tanks and their liquid scintillator payload will provide a powerful neutron rejection signal so LZ is not fooled.”

    These are just a few of the many steps being taken to ensure that LZ once again scours the universe with pristine accuracy.

    “We want to do again what we did five years ago—create the most sensitive dark matter detector in the world,” said Dr. Markus Horn, research scientist at Sanford Lab and a member of the LZ collaboration.

    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.

    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.

     
  • richardmitnick 9:04 am on October 23, 2018 Permalink | Reply
    Tags: , , East Drift ground support project completed, , , SURF - Sanford Underground Research Facility   

    From Sanford Underground Research Facility: “East Drift ground support project completed” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    October 22, 2018

    Constance Walter

    More than 6,500 rock bolts, 1,100 pounds of wire mesh went into rehab project on 4850 Level.

    1
    The East Drift of the 4850 Level. Matthew Kapust

    The numbers tell the story.

    For more than two years, Fritz Reller, a member of the Underground Maintenance Crew (UMC), focused on installing ground support in the East Drift of the 4850 Level. He removed thousands of rocks, drilled more than 6,500 holes for rock bolts and secured over 1,100 panels of welded wire mesh through an area that covers approximately 1,850 feet between the Yates Shaft and Four Winze Wye.

    “It was a challenging job, but we couldn’t be happier with the outcome,” said Bryce Pietzyk, underground access director. “The quality Fritz puts into the project is obvious. He is very dedicated and got the project done safely.”

    The drift is used to convey scientists, crews, contractors and equipment via locomotive between the Davis and Ross Campuses.

    “The completion of the project ensures the ground will be stable and safe for all of our stakeholders,” said Mike Headley, executive director for Sanford Lab. “Fritz has been doing this kind of work for years. He is meticulous, and the work is of the highest quality.”

    Luke Scott, UMC lead, knows first-hand what goes into ground support. He worked for nearly 14 years at Homestake and 10 years at Sanford Lab.

    His team, which included infrastructure technicians Reller, Mike Oates and Bill Geffre, excavated the Davis Campus and helped prepare the space for outfitting. They also put in ground support for CASPAR (Compact Accelerator System for Performing Astrophysical Research) and the Black Hills State University Underground Campus, both existing spaces once used as shops and maintenance areas by Homestake.

    The work is physically challenging. Crews must first bar down the drift to remove any loose rock. They use jackleg drills that weigh more than 100 pounds to drill thousands of holes in hard rock then drive the rock bolts. All to make the space safe for stakeholders.

    “We have to make sure we do an excellent job preparing every area and making sure we stay safe,” Scott said. “It all comes with experience and Fritz has got a lot of that.”

    For more than two years, Reller barred, meshed and bolted along an 1,850-foot drift on the 4850 Level of Sanford Lab. He did it meticulously and without a single safety incident.

    “That says a lot for the kind of work Fritz does,” Pietzyk added. “I’m really proud of him and the rest of the team, too. They all take their work seriously and do a great job.”

    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.

    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.

     
  • richardmitnick 9:33 am on October 15, 2018 Permalink | Reply
    Tags: A Hefty WIMP Detector, , Large Underground Xenon (LUX) experiment, LZ experiment a $70 million upgrade and unification of the LUX and the UK-based ZEPLIN III teams, SURF - Sanford Underground Research Facility, , Xenon1T project at Gran Sasso located in the Abruzzo region of central Italy   

    From UC Santa Barbara: “A Hefty WIMP Detector” 

    UC Santa Barbara Name bloc
    From UC Santa Barbara

    October 15, 2018
    Harrison Tasoff

    Installation of a detector designed by UC Santa Barbara physicists is underway at the LZ dark matter experiment.

    LBNL LZ project at SURF, Lead, SD, USA

    LZ Dark Matter Experiment at SURF lab

    UC Santa Barbara postdoctoral scientist Sally Shaw stands with one of the four large acrylic tanks fabricated for the LZ dark matter experiment’s outer detector.

    There’s a big hole in our current understanding of what makes up the universe. Normal matter — the stuff in people, planets and pulsars — can account for only 16 percent of the mass in the universe. Scientists know there’s more out there because they can see its effects: Its gravity bends light from distant sources and keeps galaxies from spinning themselves apart.

    Coma cluster via NASA/ESA Hubble

    Fritz Zwicky, Fritz Zwicky, the Father of Dark Matter research public domain

    Fritz Zwicky discovered Dark Matter by his study of the Coma Cluster. His work was aided by Vera Rubin

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)

    Dark matter doesn’t appear to interact with normal matter via electromagnetism or through the strong nuclear force, which is known for binding particles together in the nuclei of atoms. Aside from gravity, that leaves one other force: the weak force, which is involved in radioactive decay. A leading hypothesis is that dark matter may be composed of exotic particles that have a high mass and interact with normal matter only through gravity and the weak force. Scientists call these weakly interacting massive particles, or WIMPs, and the search is on to find out if they exist.

    UC Santa Barbara physics professors Harry Nelson and Michael Witherell (now the director of Lawrence Berkeley Laboratory) have researched dark matter since the 1980s. About 10 years ago, some of their collaborators proved that liquid xenon was a superb medium for detecting WIMPs. Nelson and Witherell joined to help put together the Large Underground Xenon (LUX) experiment.

    The experiment was essentially a 32-gallon vat of liquid xenon that could detect when a single xenon atom was struck by a WIMP. It was located at the Sanford Underground Research Facility, roughly a mile under the Black Hills of South Dakota. This mile of rock shields the detector from the stream of particles that shower down on Earth’s surface every day. “We led the world in sensitivity in the hunt for WIMPs,” said Nelson.

    Since LUX came online in 2013, a number of similar, larger detectors in Italy and China joined the hunt. An international race was underway, and the LUX team proposed the LZ experiment, a $70 million upgrade and unification of the LUX and the UK-based ZEPLIN III teams. The LZ detector is designed to leapfrog the competition, and will contain 850 gallons of liquid xenon, about 27 times the volume of LUX.

    The new experiment will be so sensitive that it has to account for false positives from solar neutrinos, explained Nelson. Neutrinos are particles so ephemeral that co-discoverer and Nobel laureate Frederick Reines called them “the most tiny quantity of reality ever imagined by a human being.” Trillions of them pass straight through your body every second.

    Nelson, Witherell and a team of engineers and students designed the outer detector for the LZ experiment, starting in 2012. The outer detector consists primarily of four 12-foot-tall, clear acrylic tanks that will surround the core detector. The fabrication of these tanks proved a challenging, Nelson noted, giving credit to Reynolds Polymer Technology of Grand Junction, CO, who took on the task. The scientists will fill these tanks with a liquid that produces a small flash when hit by a particle, allowing them to distinguish a WIMP event from background radiation coming from radioactive impurities in the detector or the few conventional particles that manage to penetrate the rock above.

    Two of the four tanks, recently completed, will make the long journey underground later this month. “The logistics of building a large apparatus underground, accessible only by narrow tunnels, forces us to install the outer detector prior to the LZ liquid xenon detector,” Nelson said.

    The LZ experiment is scheduled to turn on in 2020 and should grab the lead in the hunt for WIMPs back from the Italians, whose current Xenon1T project contains about 271 gallons of liquid xenon. The Xenon1T team has plans for an upgrade to rival LZ, however, so the race is still on.

    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

    “The incredible intellectual odyssey of the past 100,000 years, starting with modern humans questioning the nature of the element gold up to the very recent discovery of the Higgs particle, covers only one-sixth of the matter in the universe,” said Nelson. “Should LZ see a WIMP signal, it will mark the beginning of a new era of exploration and discovery.”

    Additional project collaborators at UC Santa Barbara include postdoctoral scientist Sally Shaw; engineers Susanne Kyre, Dano Pagenkopf and Dean White; and graduate students Scott Haselschwardt, Curt Nehrkorn and Melih Solmaz. The LZ group is supported by the U.S. Department of Energy’s Office of High Energy Physics.

    See the full article here .


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

    Stem Education Coalition

    UC Santa Barbara Seal
    The University of California, Santa Barbara (commonly referred to as UC Santa Barbara or UCSB) is a public research university and one of the 10 general campuses of the University of California system. Founded in 1891 as an independent teachers’ college, UCSB joined the University of California system in 1944 and is the third-oldest general-education campus in the system. The university is a comprehensive doctoral university and is organized into five colleges offering 87 undergraduate degrees and 55 graduate degrees. In 2012, UCSB was ranked 41st among “National Universities” and 10th among public universities by U.S. News & World Report. UCSB houses twelve national research centers, including the renowned Kavli Institute for Theoretical Physics.

     
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