Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session T12: Dark Matter Instrumentation II |
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Sponsoring Units: DPF DNP Chair: Leslie Rosenberg, University of Washington Room: Plaza Court 1 |
Monday, April 15, 2013 3:30PM - 3:42PM |
T12.00001: ABSTRACT WITHDRAWN |
Monday, April 15, 2013 3:42PM - 3:54PM |
T12.00002: Measurement of Scintillation Efficiency of Low Energy Nuclear Recoils in Liquid Argon H. Cao, H.O. Back, F. Calaprice, C. Galbiati, P. Meyers, B. Rossi, L. Grandi, W.H. Lippincott, B. Loer, F. DeJongh, S. Pordes, J. Yoo, C. Kendziora, D. Montanari, T. Alexander, A. Cocco, G. Fiorillo, H. Wang, Y. Meng, C.J. Martoff, C. Love, P. Collon, W. Tan, C. Ghag, L. Manenti Particle detectors based on liquid argon (LAr) have become an appealing option for direct WIMP detection. The detection threshold for recoiling Ar nuclei produced by WIMPs required precise determination, as the existing measurements of the relative scintillation efficiency of nuclear recoils carried large uncertainties at low energies. We have measured the scintillation efficiency of nuclear recoils with kinetic energy between 5.8 and 60 keV relative to that of 122 keV gamma rays from $^{57}$Co. Our experiment used a compact LAr time projection chamber in a monochromatic pulsed neutron beam obtained through $^{7}$Li(p,n)$^{7}$Be reaction. The scintillation efficiency was also measured under electric field up to 1.0 kV/cm. [Preview Abstract] |
Monday, April 15, 2013 3:54PM - 4:06PM |
T12.00003: New Measurement of the Charge and Light Yield of Low Energy Nuclear and Electronic Recoils in Liquid Xenon L.W. Goetzke, E. Aprile, R. Budnik, H.A. Contreras, A.J. Melgarejo Fernandez, J. Naganoma, G. Plante, A. Rizzo Liquid xenon detectors are one of the leading technologies in direct dark matter searches. In order to improve the precision of their energy scales, it is important to characterize the scintillation and ionization of liquid xenon at low energies, where measurements with applied electric field are few or nonexistent. At Columbia University we have built a dual-phase detector, neriX, capable of simultaneously measuring the light and charge deposits from low-energy interactions in liquid xenon. The detector was designed to optimize event vertex reconstruction while maintaining a high light detection efficiency. Far detector coincidence techniques (Compton or neutron elastic scattering) are employed to extract the light and charge yields of liquid xenon as a function of energy for different particle types. In this talk we will discuss the detector calibration and performance, and will present some preliminary results. [Preview Abstract] |
Monday, April 15, 2013 4:06PM - 4:18PM |
T12.00004: Measuring low energy nuclear recoil response in NaI(Tl) Tyana Stiegler, Clement Sofka, James White, Robert Webb An investigation of the low energy nuclear recoil response of NaI(Tl) will be discussed. The experiment uses low energy neutrons produced via the Li(p,n) reaction and utilizes a high light output NaI(Tl) crystal. The goal is to improve on published measurements at energies relevant to DAMA/LIBRA and other low-mass WIMP experiments. The experimental design and setup, shielding optimization, neutron beam calibration techniques and preliminary results will be included. [Preview Abstract] |
Monday, April 15, 2013 4:18PM - 4:30PM |
T12.00005: Energy Resolution in High Pressure Xenon Gas Using Electroluminescence in Parallel Wire Grids vs. Crossed Wire Meshes Clement Sofka, James White Several rare event searches ($e.g.$ detection of dark matter particles and neutrinoless double beta decay) are ongoing around the globe utilizing electroluminescent (EL) light collection from noble elements in drift chambers. These detectors use various wire geometries to achieve an EL gap that is optimized for light production, light collection, and energy resolution. We investigate the energy resolution of a parallel wire geometry and compare it to an EL gap composed of two crossed meshes in a high pressure gaseous xenon (GXe) drift chamber. The design, construction and results will be discussed. [Preview Abstract] |
Monday, April 15, 2013 4:30PM - 4:42PM |
T12.00006: Efficiency Studies and Simulations of a Neutron Background Veto for Dark Matter Detectors Shawn Westerdale, Emily Shields, Jingke Xu, Frank Calaprice In direct WIMP dark matter detection experiments, neutrons from cosmogenic sources and nuclear reactions in detector materials can provide backgrounds indistinguishable from WIMP signals. To reduce this background, an active neutron veto filled with a boron-loaded scintillator is being developed. The scintillator used will be pseudocumene, mixed with trimethyl borate as a boron source, and a PPO wavelength shifter. Such a veto would detect neutrons in the volume surrounding the detector, allowing coincident background events in the detector to be rejected. Neutrons are captured by the $^{10}$B with a high cross section, resulting in an $\alpha$ and $^7$Li. The scintillation from the nuclear products is heavily quenched to an equivalent electron energy as low as 50 keV. To detect this, it is necessary to have high light collection efficiency. To model the neutron veto concept, light yield measurements were taken for a small prototype filled with the scintillator mixture and lined with a Lumirror reflector. These results were reproduced in GEANT4 and in an independent simulation. We then applied the simulations to the DarkSide-50 neutron veto to predict its neutron rejection power. Results from measurements taken with the prototype and from the simulation will be presented. [Preview Abstract] |
Monday, April 15, 2013 4:42PM - 4:54PM |
T12.00007: Demonstration of the Prototype BetaCage, an Ultra-sensitive Screener for Surface Contamination A. Rider, Z. Ahmed, S. Golwala, R. Nelson, A. Zahn, R. Bunker, M. Kos, R.W. Schnee, B. Wang, D.R. Grant Material screening for low-energy betas and alphas is necessary for rare-event-search experiments, such as dark matter and neutrinoless double-beta decay searches where surface radiocontamination is a significant background. The BetaCage, a gaseous neon time-projection chamber, has been proposed as a screener for emitters of low-energy betas and alphas to which existent screening facilities are insufficiently sensitive. We have constructed and characterized a prototype of the BetaCage to demonstrate the viability of constructing a time-projection chamber out of materials consistent with radio-purity. The prototype has demonstrated sufficient energy resolution and stability to indicate the success of our basic design. We report on the details of the detection characteristics of the prototype BetaCage. [Preview Abstract] |
Monday, April 15, 2013 4:54PM - 5:06PM |
T12.00008: Expected Backgrounds of the BetaCage, an Ultra-sensitive Screener for Surface Contamination Boqian Wang, Raymond Bunker, Richard Schnee, Michael Bowles, Marek Kos, Zeeshan Ahmed, Sunil Golwala, Robert Nelson, Darren Grant Material screening for low-energy betas and alphas is necessary for rare-event-search experiments, such as dark matter and neutrinoless double-beta decay searches where surface radiocontamination has become a significant background. The BetaCage, a gaseous neon time-projection chamber, has been proposed as a screener for emitters of low-energy betas and alphas to which existing screening facilities are insufficiently sensitive. The expected sensitivity is 0.1 betas / (keV m$^2$ day) and 0.1 alphas / (m$^2$ day). Expected backgrounds are dominated by Compton scattering of external photons in the sample to be screened; radioassays and simulations indicate backgrounds from detector materials and radon daughters should be subdominant. We will report on details of the background simulations and the detector design that allows discrimination to reach these sensitivity levels. [Preview Abstract] |
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