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  • richardmitnick 9:27 am on September 10, 2019 Permalink | Reply
    Tags: "The nuts and bolts of experimental science", LBNL LUX-ZEPLIN dark matter experiment at Sanford Underground Research Facility in South Dakota,   

    From Sanford Underground Research Facility: “The nuts and bolts of experimental science” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    September 9, 2019
    Erin Broberg

    Derek Lucero, left, shakes hands with Tomasz Biesiadzinski, right, after the team completed the extensive cabling of the LUX-ZEPLIN PMT arrays.
    Matthew Kapust

    The challenge of experimental science is this: Build machines capable of testing abstract theories. Experimental researchers must design functional machines that can “see” rare interactions and express those interaction with numerical data. That data, in turn, feeds ever-evolving theoretical models.

    This fluctuation between abstract ideas and the nuts and bolts of building an experiment requires the worlds of physics and engineering to merge. Engineers at the Sanford Underground Research Facility (Sanford Lab), whether working directly with experiments or bolstering the facility itself, provide a much-needed link between theory and function.

    The first of its kind

    Over the past year, Derek Lucero transitioned from labor-intensive work in the Ross Shaft to assembling the pieces of a highly intricate experiment. For the last 10 months, Lucero and Jeff Barthel, both engineering technical associates, provided engineering support to the LUX-ZEPLIN (LZ) dark matter collaboration during the assembly of the innermost piece of the experiment, the Time Projection Chamber (TPC), in a class-100 cleanroom.

    LZ Time Projection Chamber assembly completed
    Collaboration puts together the ‘heart’ of LUX-ZEPLIN dark matter detector
    The recently assembled LUX-ZEPLIN xenon detector in the Surface Assembly Lab cleanroom at Sanford Underground Research Facility on July 26, 2019. Photo by Matthew Kapust Sanford Underground Research Facility.

    “Trust me, there are no instruction manuals for this type of work,” Lucero said. That’s because each of the TPC’s tens of thousands of components were specifically designed and fabricated for this experiment by institutions around the world. To assemble these components, physicists and engineers converged to properly address the mechanical, optical, electrical, background and cleanliness requirements for each piece.

    Lucero helps a researcher work on an electric grid in the Surface Assembly Lab. Photo by Matthew Kapust.

    “From providing supplies to fine precision work on the innards of the LZ detector itself, the engineers have machined parts for both the underground circulation system as well as the xenon detector,” said Tomasz Biesiadzinski, a project scientist with SLAC National Accelerator Laboratory who has led the assembly effort at Sanford Lab. “They’re also the ones we rely on to connect fine circuits, fix fragile cables and install delicate detector components that would drive anyone else crazy.”

    Each day, the team met to discuss the multidimensional work before donning full-body Tyvek suits and gloves to enter the cleanroom. “As an engineer, I typically want to find solutions as quickly and efficiently as possible,” Lucero said. “Physicists, I’ve learned, approach things more cautiously, coming at the problem from every angle. This is good, because we’ve only got one shot at this. We work together to find that middle ground between thought and action.”

    “It’s two different philosophies,” said Allan Stratman, director of engineering at Sanford Lab. “Engineers want to eliminate ambiguity. We like things black and white. We see problems and want to solve them. Physicists, though, are doing theoretical work, so they thrive on ambiguity and need as much flexibility as we can afford. With the reality of the experiment coming online, those philosophies meet to make it happen and make it right.”

    The novel solutions these differing mindsets settled on led to the completion of the TPC, which will soon move to the 4850 Level, where another team of engineers has been preparing the Davis Cavern to receive it.

    Turning wrenches and learning physics

    For the time being, engineers typically outnumber physicists in the Davis Cavern. At first glance, however, you’d have difficulty telling them apart. Physicists work alongside engineers to install subsystems and structural support, including the cryogenics system and extensive cabling.

    Charles Maupin, mechanical engineer for Sanford Lab, in the Davis Campus. Photo by Mark Hanhardt.​​​​​

    “Many of the researchers don’t have backgrounds turning wrenches, running drills or cutting steel,” said Dale Curran, engineering technical associate. “I think it’s good when they have an opportunity to be onsite and do hands-on work. After this is done, it’ll be a waiting-game for half a decade as the detector collects data.”

    “The engineering team is crucial for us,” said David Woodward, a post-doctoral researcher who spent several months working with engineers to install the test cryostat for the circulation system commissioning. “They not only help us get things done, but they improve the quality of our work by filling in the gaps with their considerable skills and knowledge.”

    The learning curve goes both ways, as engineers get the chance to brush up on dark matter physics, as well.

    “The big takeaway for me is that it’s about noise cancelation,” Curran said. “We are looking for something that is very obscure and difficult to find—something you need to discern from a billion other things. Imagine being at a rock concert, trying to listen for a pin to drop. That’s the background on the surface of the earth. On the 4850 Level, it’s goes from sounding like a rock concert, to listening to the radio in your car. Here, you still have to discern from smaller backgrounds—the drums, the guitar strums, the singing voices—until you think you’ve heard the pin hitting the floor. Then, you’ve got to prove that’s really what you heard.”

    “We also provide a level of institutional memory,” Barthel said. While collaboration members visit the facility when their subsystem is ready to be installed, engineers “are here every day and our team rarely changes, giving the process much-needed continuity.”

    Ship in a bottle

    Just down the drift from the Davis Cavern’s dark matter hunt, geotechnical engineer David Vardiman is helping to prepare a space for the largest physics experiment on United States soil—or, more accurately, under it.

    “We often say we are building a ship in a bottle,” said Vardiman, who is helping prepare for excavation for the Long Baseline Neutrino Facility (LBNF). “Except the neck of this bottle is 5,000 feet long.”

    LBNF will house the Deep Underground Neutrino Experiment’s (DUNE) Far Detector on the 4850 Level in Sanford Lab, as well as the much smaller near detector at Fermilab. The DUNE detectors require intricate cryogenic technology to keep them at their operating temperature of minus 300 degrees Fahrenheit. Over the next few years, about 800,000 tons of rock will be excavated at Sanford Lab to house the detector and its complex systems.

    “The most important aspect of planning is listening to a scientist’s requirements,” Vardiman said. “Not everyone understands the vagaries of the rock—they may not realize how important a specification is. As an engineer, I have to help them verbalize all that they need. If not, we could miss out on an important detection requirement, all because we failed to pay attention.”

    Bolstering the facility infrastructure

    Some engineers have little direct interaction with experiments, but their work is nonetheless critical to the facility. Physical infrastructure projects include strengthening the Ross Shaft Headframe, providing engineering support to the Underground Maintenance Crew and Wastewater Treatment Plant.

    “Anything that moves, turns, makes noise, or breaks, that’s something we’re involved in,” said Todd Hubbard, senior project engineer.

    Laser scanners create 3-D imaging of underground areas, helping the engineering team better define each space, ventilation engineers monitor airflow through the underground matrix and electrical engineers ensure high availability and reliability of power to experiment sites and the overall facility.

    A new twist on traditional engineering

    Engineers at Sanford Lab come from varied backgrounds, from the largest machine tool builder in the western world to the production of roofing materials, to mining engineering to auto shop owner. For them, these tasks are simply novel approaches to familiar work.

    “I think our previous experience translates well into this facility,” said Jacob Davis, a mechanical engineer. His previous experience with cranes and rigging was called upon when layers of the LZ TPC needed to be stacked inside the cleanroom. “These were critical lifts. For some of them, there was a crowd of researchers looking from outside the window. One time, a researcher told me just how much the pieces in the lift cost. Regardless of the price tag on the object, though, I do the work the same. Whether it’s 10 dollars or 20 million dollars—it’s important to do it right.”

    Whether working in a cleanroom to build a sensitive detector, readying a cavern for new science or supporting the physical infrastructure of the facility, at the end of the day, the engineers are solving problems.

    “Because these problems have never been solved before, our engineers are fabricating completely new solutions,” Stratman said. “As a geek engineer, that’s pretty amazing to me. We are engineering for the sake of science; our end goal is to provide exactly the solutions scientists need.”

    Jeff Cherwinka, chief engineer for LZ, (left) and Charles Maupin, mechanical engineer for Sanford Lab (right) in the Davis Campus office space. Photo by Erin Broberg.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

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

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

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

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

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

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

    LBNL LZ project at SURF, Lead, SD, USA, will replace LUX at SURF

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

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

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

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

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

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


    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.


    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 12:41 pm on October 23, 2018 Permalink | Reply
    Tags: , , , , High-Luminosity LHC (HL-LHC) at CERN, LBNL LUX-ZEPLIN dark matter experiment at Sanford Underground Research Facility in South Dakota, LBNL/DESI Dark Energy Spectroscopic Instrument for the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson Ariz USA, SLAC Large Synoptic Survey Telescope at Cerro Pachon Chile, ,   

    From Symmetry: “The building boom” 

    Symmetry Mag
    From Symmetry

    By Diana Kwon

    Illustration by Sandbox Studio, Chicago with Ana Kova

    These international projects, selected during the process to plan the future of US particle physics, are all set to come online within the next 10 years.

    A mile below the surface at Sanford Underground Research Facility in South Dakota, crews are preparing to excavate more than 800,000 tons of rock. Once the massive caverns they’re creating are complete, they will install four modules that make up a giant particle detector for the Deep Underground Neutrino Experiment. DUNE, hosted by the US Department of Energy’s Fermi National Accelerator Laboratory, is an ambitious, international effort to study neutrinos—the tiny, elusive and yet most abundant matter particles in the universe.

    DUNE is one of several particle physics and astrophysics projects with US participation currently under some stage of construction. These include large-scale projects, such as the construction of Mu2e, the muon-to-electron conversion experiment at Fermilab, and upgrades to the Large Hadron Collider at CERN. And they include smaller ones, such as the assembly of the LZ and SuperCDMS dark matter experiments. Together, these scientific endeavors will investigate a wide range of important concepts, including neutrino mass, the nature of dark matter and cosmic acceleration.

    “In the last 10 years, there have been many facilities in the US that wound down,” says Saul Gonzalez, a program director at the National Science Foundation. “But right now we’re definitely going through a boom—it’s a very exciting time.”

    A community effort

    Members of the US particle physics community identified these projects through a regularly occurring study of the field called the Snowmass planning process, named after the Colorado village where some of the first such dialogs took place in the early 1980s.

    After the most recent Snowmass meeting in Minneapolis in 2013, the 25-member Particle Physics Project Prioritization Panel, or P5, gathered to pinpoint the most important scientific problems in particle physics and propose a 10-year plan to take them on. “Snowmass enabled us to get the questions out there as a field,” says Steven Ritz, the University of California, Santa Cruz physicist who led the P5 panel. “But we’re also aware that budgets are constrained—so P5’s job was to prioritize them.”

    P5’s report, which was published in May 2014 [PDF], outlined five key areas of study: the Higgs boson; neutrinos; dark matter; dark energy and cosmic inflation; and undiscovered particles, interactions and physical principles.

    Shorter-term efforts to address questions in these areas, such as the Mu2e experiment and the Large Synoptic Survey Telescope in Chile, both already under construction, have projected start-up dates around 2020. Longer-term plans, such as DUNE and the high-luminosity upgrade to the LHC, are expected be ready for physics in the mid to latter part of the 2020s.

    “If you look at the timeline, we don’t build everything at once, because of budget and resource constraints,” says Young-Kee Kim, a physicist at the University of Chicago and a former member of the High Energy Physics Advisory Panel, the advisory group that P5 reports to.

    Another consideration was the importance of maintaining a continual stream of data, Ritz says. “We didn’t want to have a building boom where there was no new data for 5 or 10 years.”

    Having multiple experiments at various stages of completion is important for junior scientists. “If you’re a grad student or a postdoc and you’re working on something that’s not going to have physics data until 2024, that’s kind of a problem,” says Kate Scholberg, a physicist at Duke University who was on the P5 panel.

    A staggered timeline gives junior scientists the option of working on a project like DUNE, where they can contribute to research and development, then switch to another experiment where data is available for analysis.

    “Being in a construction phase does have some short-term challenges, but it’s really important as an investment for the future,” Scholberg says. “Because if you stop constructing, then eventually you’re not going to have any more data.”

    Global contributions

    The United States is not undertaking these experiments alone. “Every experiment is really an international collaboration,” Gonzalez says.

    The DUNE collaboration, for example, already includes more than 1100 scientists from 32 countries and counting. And although the Long-Baseline Neutrino Facility, the future home of DUNE, will be in the US, researchers are currently building prototype detectors for the project at the CERN research center in Europe.

    More than 1700 US scientists participate in research at the LHC at CERN; many of them are currently working on future upgrades to the accelerator and its experiments. Although LSST will operate on a mountaintop in Chile, its gigantic digital camera is being assembled at SLAC National Accelerator Laboratory using parts from institutions elsewhere in the United States and in France, Germany and the UK.

    Smaller experiments also have a global presence. Dark matter experiment SuperCDMS, a 23-institution collaboration led by SLAC, will be located at SNOLAB underground laboratory in Ontario and has members in Canada, France and India.

    People with specialized expertise are needed to build the apparatus for these experiments. For example, Fermilab’s Proton Improvement Plan-II, a project to upgrade the lab’s particle accelerator complex to provide protons beams for DUNE, requires individuals with expertise in superconducting radio-frequency technology. “We’re tapping into the SRF expertise around the world to build this,” says Michael Procario, the Director of the Facilities Division in the Office of High Energy Physics within DOE’s Office of Science.

    These DOE-supported endeavors—and the theory and data analysis that go along with them—will likely keep scientists busy until 2035 and beyond. “All the experiments are going to give us definitive answers. Even a null result will give us important information,” Ritz says. “I think it’s a great time for physics.”

    The experiments:

    Muon g-2

    FNAL Muon g-2 studio

    This experiment will measure the magnetic moment of a muon, a subatomic particle 200 times more massive than an electron, in an attempt to identify physics beyond the Standard Model.

    Location: Fermilab, Illinois, United States
    Lead institution: Fermilab
    Currently running

    Axion Dark Matter Experiment (ADMX-Gen 2)

    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington

    U Washington ADMX

    Physicists are probing for signs of axions, hypothetical low-mass dark matter particles at the University of Washington-based ADMX detector.

    Location: University of Washington, United States
    Lead institution: University of Washington
    Currently running

    Physicists will use Mu2e to search for the never-observed direct conversion of a muon into an electron, a process predicted by theories beyond the Standard Model.

    FNAL Mu2e facility under construction

    FNAL Mu2e solenoid

    Location: Fermilab, Illinois, United States
    Lead institution: Fermilab
    Scheduled start-up: 2020


    LBNL LZ project at SURF, Lead, SD, USA

    LZ Dark Matter Experiment at SURF lab

    A liquified xenon detector surrounded by 70,000 gallons of water will be located more than 4000 feet underground at the Sanford Underground Research Facility, where researchers will hunt for interactions between matter and dark matter.

    Location: Sanford Lab, South Dakota, United States
    Lead institution: Berkeley Lab
    Scheduled start-up: 2020

    Dark Energy Spectroscopic Instrument (DESI)

    LBNL/DESI Dark Energy Spectroscopic Instrument for the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, Ariz, USA

    NOAO/Mayall 4 m telescope at Kitt Peak, Arizona, USA, Altitude 2,120 m (6,960 ft)

    Scientists will measure the effect of dark energy on cosmic expansion at the 4-meter Mayall Telescope at Kitt Peak National Observatory in Arizona.

    Location: Kitt Peak National Observatory, Arizona, United States
    Lead institution: Berkeley Lab
    Scheduled start-up: 2021

    Super Cyogenic Dark Matter Search (SuperCDMS)

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

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

    SLAC SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)

    SLAC SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)

    Physicists will hunt for dark matter particles with a cryogenic germanium detector located deep underground at SNOLAB in Canada.

    Location: SNOLAB, Ontario, Canada
    Lead institution: SLAC
    Scheduled start-up: Early 2020s

    Large Synoptic Survey Telescope (LSST)


    LSST Camera, built at SLAC

    LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    The 8-meter Large Synoptic Survey Telescope, situated in northern Chile, will observe the whole accessible sky hundreds of times over 10 years to produce the deepest, widest image of the universe to date. This will allow physicists to probe questions about dark energy, dark matter, galaxy formation and more.

    Location: Cerro Pachon, Chile
    Lead institution: SLAC
    Scheduled start-up: Early 2020s

    Proton Improvement Pla-II (PIP-II)

    Upgrades to the Fermilab accelerator complex, including the construction of a 175-meter-long superconducting linear particle accelerator, will create the high-intensity proton beam that will produce beams of neutrinos for DUNE.

    Location: Fermilab, Illinois, United States
    Lead institution: Fermilab
    Scheduled start-up: mid-2020s

    Deep Underground Neutrino Experiment (DUNE)

    CERN Proto DUNE Maximillian Brice

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

    SURF DUNE LBNF Caverns at Sanford Lab

    Scientists will send the world’s most powerful beam of neutrinos through two sets of detectors separated by 800 miles—one at the source of the beam at Fermilab in Illinois and the other at Sanford Underground Research Facility in South Dakota—to help scientists address fundamental concepts in particle physics, such as neutrino mass, matter-antimatter asymmetry, proton decay and black hole formation.

    Location: Fermilab, Illinois and Sanford Lab, South Dakota, United States
    Lead institution: Fermilab
    Scheduled partial start-up (with two detector modules): 2026

    High-Luminosity LHC (HL-LHC)


    CERN map

    CERN LHC Tunnel

    CERN LHC particles

    An upgrade to CERN’s Large Hadron Collider will increase its luminosity—the number of collisions it can achieve—by a factor of 10. More collisions means more data and a higher probability of spotting rare events. The LHC experiments will receive upgrades to manage the higher collision frequency.

    Location: CERN, near Geneva, Switzerland
    Lead institution: CERN
    Scheduled start-up: 2026

    See the full article here .


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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 4:11 pm on October 16, 2018 Permalink | Reply
    Tags: , , , Fermilab’s Aaron Chou is leading a multi-institutional consortium to apply the techniques of quantum metrology to the problem of detecting axion dark matter, Finding an axion is a delicate endeavor even compared to other searches for dark matter, HAYSTAC axion experiment at Yale, LBNL LUX-ZEPLIN dark matter experiment at Sanford Underground Research Facility in South Dakota, , , , , The qubit advantage at FNAL,   

    From Symmetry: “Looking for dark matter using quantum technology” 

    Symmetry Mag
    From Symmetry

    Jim Daley

    Photo by Reidar Hahn, Fermilab

    For decades, physicists have been searching for dark matter, which doesn’t emit light but appears to make up the vast majority of matter in the universe. Several theoretical particles have been proposed as dark matter candidates, including weakly interacting massive particles—called WIMPs—and axions.

    Fermilab’s Aaron Chou is leading a multi-institutional consortium to apply the techniques of quantum metrology to the problem of detecting axion dark matter. The project, which brings together scientists at Fermilab, the National Institute of Standards and Technology, the University of Chicago, University of Colorado and Yale University, was recently awarded $2.1 million over two years through the Department of Energy’s Quantum Information Science-Enabled Discovery (QuantISED) program, which seeks to advance science through quantum-based technologies.

    If the scientists succeed, the discovery could solve several cosmological mysteries at once.

    “It’d be the first time that anybody had found any direct evidence of the existence of dark matter,” says Fermilab’s Daniel Bowring, whose work on this effort is supported by a DOE Office of Science Early Career Research Award. “Right now, we’re inferring the existence of dark matter from the behavior of astrophysical bodies. There’s very good evidence for the existence of dark matter based on those observations, but nobody’s found a particle yet.”

    The axion search

    Finding an axion would also resolve a discrepancy in particle physics called the strong CP problem. Particles and antiparticles are “symmetrical” to one another: They exhibit mirror-image behavior in terms of electrical charge and other properties.

    The strong force—one of the four fundamental forces of nature—obeys CP symmetry. But there’s no reason, at least in the Standard Model of physics, why it should. The axion was first proposed to explain why it does.

    Finding an axion is a delicate endeavor, even compared to other searches for dark matter. An axion’s mass is vanishingly low—somewhere between a millionth and a thousandth of an electronvolt. By comparison, the mass of a WIMP is expected to be between a trillion and quadrillion times more massive—in the range of a billion electronvolts—which means they’re heavy enough that they could occasionally produce a signal by bumping into the nuclei of other atoms. To look for WIMPs, scientists fill detectors with liquid xenon (for example, in the LUX-ZEPLIN dark matter experiment at Sanford Underground Research Facility in South Dakota) or germanium crystals (in the SuperCDMS Soudan experiment in Minnesota [not current, now at SNOLAB a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario]) and look for indications of such a collision.

    LBNL Lux Zeplin project at SURF

    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.

    LZ Dark Matter Experiment at SURF lab

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

    SLAC SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)

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

    “You can’t do that with axions because they’re so light,” Bowring says. “So the way that we look for axions is fundamentally different from the way we look for more massive particles.”

    When an axion encounters a strong magnetic field, it should—at least in theory—produce a single microwave-frequency photon, a particle of light. By detecting that photon, scientists should be able to confirm the existence of axions. The Axion Dark Matter eXperiment, ADMX, at the University of Washington and the HAYSTAC experiment at Yale are attempting to do just that.

    ADMX Axion Dark Matter Experiment at the University of Washington

    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington

    U Washington ADMX

    Yale HAYSTAC axion dark matter experiment

    Yale Haloscope Sensitive To Axion CDM -HAYSTAC Experiment a microwave cavity search for cold dark matter (CDM)

    Those experiments use a strong superconducting magnet to convert axions into photons in a microwave cavity. The cavity can be tuned to different resonant frequencies to boost the interaction between the photon field and the axions. A microwave receiver then detects the signal of photons resulting from the interaction. The signal is fed through an amplifier, and scientists look for that amplified signal.

    “But there is a fundamental quantum limit to how good an amplifier can be,” Bowring says.

    Photons are ubiquitous, which introduces a high degree of noise that must be filtered from the signal detected in the microwave cavity. And at higher resonant frequencies, the signal-to-noise ratio gets progressively worse.

    Both Bowring and Chou are exploring how to use technology developed for quantum computing and information processing to get around this problem. Instead of amplifying the signal and sorting it from the noise, they aim to develop new kinds of axion detectors that will count photons very precisely—with qubits.

    Aaron Chou works on an FNAL experiment that uses qubits to look for direct evidence of dark matter in the form of axions. Photo by Reidar Hahn, Fermilab

    The qubit advantage

    In a quantum computer, information is stored in qubits, or quantum bits.

    Quantum computing – IBM

    A qubit can be constructed from a single subatomic particle, like an electron or a photon, or from engineered metamaterials such as superconducting artificial atoms. The computer’s design takes advantage of the particles’ two-state quantum systems, such as an electron’s spin (up or down) or a photon’s polarization (vertical or horizontal). And unlike classical computer bits, which have one of only two states (one or zero), qubits can also exist in a quantum superposition, a kind of addition of the particle’s two quantum states. This feature has myriad potential applications in quantum computing that physicists are just starting to explore.

    In the search for axions, Bowring and Chou are using qubits. For a traditional antenna-based detector to notice a photon produced by an axion, it must absorb the photon, destroying it in the process. A qubit, on the other hand, can interact with the photon many times without annihilating it. Because of this, the qubit-based detector will give the scientists a much higher chance of spotting dark matter.

    “The reason we want to use quantum technology is that the quantum computing community has already had to develop these devices that can manipulate a single microwave photon,” Chou says. “We’re kind of doing the same thing, except a single photon of information that’s stored inside this container is not something that somebody put in there as part of the computation. It’s something that the dark matter put in there.”

    Light reflection

    Using a qubit to detect an axion-produced photon brings its own set of challenges to the project. In many quantum computers, qubits are stored in cavities made of superconducting materials. The superconductor has highly reflective walls that effectively trap a photon long enough to perform computations with it. But you can’t use a superconductor around high-powered magnets like the ones used in Bowring and Chou’s experiments.

    “The superconductor is just ruined by magnets,” Chou says. Currently, they’re using copper as an ersatz reflector.

    “But the problem is, at these frequencies the copper will store a single photon for only 10,000 bounces instead of, say, a billion bounces off the mirrors,” he says. “So we don’t get to keep these photons around for quite as long before they get absorbed.”

    And that means that they don’t stick around long enough to be picked up as a signal. So the researchers are developing another, better photon container.

    “We’re trying to make a cavity out of very low-loss crystals,” Chou says.

    Think of a windowpane. As light hits it, some photons will bounce off it, and others will pass through. Place another piece of glass behind the first. Some of the photons that passed through the first will bounce off the second, and others will pass through both pieces of glass. Add a third layer of glass, and a fourth, and so on.

    “Even though each individual layer is not that reflective by itself, the sum of the reflections from all the layers gives you a pretty good reflection in the end,” Chou says. “We want to make a material that traps light for a long time.”

    Bowring sees the use of quantum computing technology in the search for dark matter as an opportunity to reach across the boundaries that often keep different disciplines apart.

    “You might ask why Fermilab would want to get involved in quantum technology if it’s a particle physics laboratory,” he says. “The answer is, at least in part, that quantum technology lets us do particle physics better. It makes sense to lower those barriers.”

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

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