Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session HD: Mini-symposium on Nuclear Double Beta Experiments II |
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Chair: Michael Miller, University of Washington Room: Sweeny D |
Friday, November 5, 2010 10:30AM - 10:42AM |
HD.00001: Toward a tonne-scale germanium neutrinoless double beta decay experiment David Steele A tonne-scale Ge neutrinoless double beta decay experiment, motivated by the desire to explore the Majorana neutrino mass regime indicated by atmospheric neutrino oscillation results, would need to achieve O(100) smaller background rates beyond those expected in the current generation of experiments. The Majorana and GERDA collaborations are pursing two different Ge-based techniques with the intention of working together on a future tonne-scale experiment. I will discuss the background and technical requirements of such an experiment, present possible shielding configurations based on the GERDA and Majorana approaches, and outline preliminary plans for such an experiment at the Deep Underground Science and Engineering Laboratory (DUSEL). [Preview Abstract] |
Friday, November 5, 2010 10:42AM - 10:54AM |
HD.00002: Status of the EXO-200 double beta decay search Ryan McLellan A 200-kg low-background liquid Xe double beta decay detector (EXO-200) has been installed underground at the WIPP facility outside Carlsbad, NM. EXO-200 is expected to provide the first measurement of the two-neutrino decay mode of 136Xe, as well as place competitive limits on the possible neutrinoless mode. EXO-200 is also serving as a large prototype for a future ton-scale xenon detector. The detector is complete and undergoing initial operations. An instrumentation run with natural Xe is planned before data-taking with enriched Xe (80{\%} enrichment). [Preview Abstract] |
Friday, November 5, 2010 10:54AM - 11:06AM |
HD.00003: Development of an RIS probe for barium tagging for EXO Karl Twelker Resonance Ionization Spectroscopy (RIS) has been shown to be a highly efficient method of selective ionization. We are investigating RIS as part of a high-efficiency single ion transport method to retrieve barium ions produced in double beta decay of xenon-136 and inject them in a ion trap where they are identified via optical spectroscopy. Highly efficient Ba-tagging would substantially reduce the background due to radioactive impurities in very large double-beta decay experiments, which limits the current generation of experiments. RIS is used to re-ionize the Ba atoms after they are desorbed from the substrate on which they had been captured. [Preview Abstract] |
Friday, November 5, 2010 11:06AM - 11:18AM |
HD.00004: EXO barium tagging R{\&}D: identification in solid Xe Brian Mong To eliminate all backgrounds and reach the 10meV level of neutrino mass sensitivity, it is desired for the next generation EXO experiment to be able to identify the $^{136}$Ba daughter nucleus in coincidence with candidate neutrinoless double beta decays. A few techniques involving laser-induced fluorescence of the Ba daughter are being developed to accomplish the detection. One technique involves freezing the Ba$^{+}$ ion in a small amount of surrounding Xe on a cryogenic probe, and looking for the characteristic fluorescence of Ba$^{+}$ or Ba in solid xenon. Progress on a technique where laser light is delivered by a fiber down the probe and fluorescence photons are collected back up the same fiber will be described. The current sensitivity is around 10$^{4}$ Ba atoms on a sapphire window, and there is good reason to believe that this sensitivity could be improved by 10$^{4}$ using a fiber. Indeed detection at the single molecule level has already been reached with a fiber probe. [Preview Abstract] |
Friday, November 5, 2010 11:18AM - 11:30AM |
HD.00005: Update on External Background Characterization of Homestake Mine for Sanford Lab and DUSEL Chao Zhang, Dongming Mei, Keenan Thomas, Fred Gray, Jaret Heise, Dan Durben Measuring and monitoring external sources of background at Sanford Lab/DUSEL are important to the planned low background experiments. The fluxes of cosmic-ray muon, gamma-ray, neutron, and radon at several levels of depth are being measured for more than one year at the Homestake Mine. We report the updated results on: (1) cosmic-ray muon flux; (2) the measurement of long-term high energy gamma ray induced by muon bremsstrahlung process; (3) neutron flux; and radon survey. [Preview Abstract] |
Friday, November 5, 2010 11:30AM - 11:42AM |
HD.00006: A cryogenic search for neutrinoless double beta decay Daniel Lenz The Cryogenic Underground Observatory for Rare Events, the CUORE experiment, employs the bolometric detector technique to search for neutrinoless double beta decay ($0\nu \beta \beta$) of $\rm ^{130}Te$. Since the halflife ($T_{1/2}$) for $0\nu \beta \beta$ of $\rm ^{130}Te$ is larger than $T_{1/2} \ge 3.0 \cdot 10^{24}$\,y (90\%C.L.) a high signal detection efficiency and an extremely low background count rate in the region of interest around the Q-value of $2527$\,keV is necessary. Large detectors made from natural $\rm TeO_{2}$ with an isotopic fraction of $33.8\%$ of $\rm ^{130}Te$ and a total active detector mass of $750$\,kg will be used as source and detector at the same time, resulting in a high signal detection efficiency. Bolometers provide a good energy resolution and have low intrinsic contaminations, which makes them an excellent detector for searches for $0\nu \beta \beta$. Since the energy response of the detector system is not linear and the detectors have long recovery times, special requirements have to be met by the calibration system. In addition, the sources have to be inserted into the cryostat and cooled from 300\,K to approx.~4\,K for each calibration, to meet heat load specifications. The CUORE experiment is currently under construction at the Gran Sasso National Laboratory, Italy. The experimental techniques, R\&D activities, the current status of the experiment and the anticipated sensitivity are reviewed. [Preview Abstract] |
Friday, November 5, 2010 11:42AM - 11:54AM |
HD.00007: Ionization Yield of Low-Energy Nuclear Recoils in a Dual-Phase Argon Detector Tenzing Joshi, Adam Bernstein, Michael Foxe, Chris Hagmann, Igor Jovanovic, Kareem Kazkaz, Samuele Sangiorgio Dual-phase argon detectors are the choice of several direct Dark Matter searches and have been proposed for detection of coherent neutrino-nucleus scattering (CNS). CNS is an as-yet undetected flavor-blind interaction predicted by the Standard Model. A small dual-phase argon detector, $\sim $250 g active mass, is being built at Lawrence Livermore National Laboratory to investigate the ionization yield of nuclear recoils in the energy range relevant to CNS detection, sub-10 keV. Two measurements are currently planned for this detector. The first will utilize elastic neutron scattering, taking advantage of the 80-keV resonance in $^{40}$Ar, to measure ionization yield at 8 keV. The second will employ nuclear resonance fluorescence on $^{40}$Ar, as a source of nuclear recoils, to map to ionization yield from 0.1-6 keV. Requirements of CNS observation are discussed along with detector commissioning and preparations for both planned measurements. [Preview Abstract] |
Friday, November 5, 2010 11:54AM - 12:06PM |
HD.00008: Segmented CdWO4 detector for low background experiments at DUSEL Dongming Mei, Yongchen Sun, Alyssa Day, Keenan THomas, Oleg Perevozchikov We propose to develop a segmented CdWO$_{4}$ scintillator array for detecting geo-neutrinos, neutrinoless double-beta, and dark matter. The detection of geo-neutrinos can shed light on the sources of the terrestrial heat flow, on the present composition, and on the origins of the Earth. The development of a new technique to detect geo-neutrinos through charge current antineutrino capture processes on $^{106}$Cd is very interesting. This target allows us to detect all of geo-neutrinos from uranium, thorium, and potassium decays. When it is built, the detector can be also used to detect neutrinoless double-beta decay with $^{116}$Cd. Both enriched $^{106}$Cd and $^{116}$Cd can be used to search for dark matter from the Universe. This paper will present R$\wp$D results on the energy response of gamma-rays and neutrons from three small CdWO$_{4}$ detectors. [Preview Abstract] |
Friday, November 5, 2010 12:06PM - 12:18PM |
HD.00009: Argon Depletion for a Large Scale Dark Matter Detector Dana Byram, Jason Spaans, Dongming Mei, Yongchen Sun, Christina Keller, Dustin Nowotny Our project intends to provide argon depleted of $^{39}$Ar by utilizing established thermal diffusion methods for isotopic separation. The depleted argon can then be used as a target material for next generation large scale dark matter detectors. Thermal diffusion exploits an established temperature gradient to produce a concentration gradient along the length of a vertical column. In this concentration gradient, the heavier isotopes accumulate at the bottom end of the column and the lighter isotopes at the top. We have built an automated twenty column thermal diffusion system. Each three meter column consists of a copper tube encasing a tungsten wire which is heated to 1200 K. The copper tube is surrounded by a water bath which is maintained at a temperature of 300 K, thus establishing a temperature gradient between the copper column and the tungsten wire. We expect to deplete the $^{39}$Ar isotope by a factor of 10 with the current design with the ultimate goal of a depletion factor of 100. The results of this effort will be reported utilizing the more abundant isotope $^{36}$Ar. In addition, the current effort for obtaining $^{39}$Ar results will be presented. [Preview Abstract] |
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