Bulletin of the American Physical Society
APS April Meeting 2014
Volume 59, Number 5
Saturday–Tuesday, April 5–8, 2014; Savannah, Georgia
Session Y13: Axion and Dark Matter III |
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Sponsoring Units: DPF Chair: Nick Hadley, University of Maryland Room: 101 |
Tuesday, April 8, 2014 1:30PM - 1:42PM |
Y13.00001: Fast neutron measurement at Soudan Mine using a large liquid scintillation detector Chao Zhang, Dongming Mei Characterizing neutron background is extremely important to the success of rare-event physics searching for neutrinoless double-beta decay and dark matter searches. Measuring the energy spectrum of fast neutrons for an underground laboratory is difficult and it requires intensive R\&D for a given technology. EJ-301 liquid scintillator(known also as NE-213) is implemented as the target for a 12 liter neutron detector fabricated at the University of South Dakota. The light output response to atmospheric neutrons from a few MeV up to $\sim$ 70 MeV has been calibrated for this detector. The detector has been taking data at Soudan Mine for over two years. We report the measured muon-induced neutrons in this paper. [Preview Abstract] |
Tuesday, April 8, 2014 1:42PM - 1:54PM |
Y13.00002: Low-background Gamma Spectroscopy at Sanford Underground Laboratory Christopher Chiller, Angela Alanson, Dongming Mei Rare-event physics experiments require the use of material with unprecedented radio-purity. Low background counting assay capabilities and detectors are critical for determining the sensitivity of the planned ultra-low background experiments. A low-background counting, LBC, facility has been built at the 4850-Level Davis Campus of the Sanford Underground Research Facility to perform screening of material and detector parts. Like many rare event physics experiments, our LBC uses lead shielding to mitigate background radiation. Corrosion of lead brick shielding in subterranean installations creates radon plate-out potential as well as human risks of ingestible or respirable lead compounds. Our LBC facilities employ an exposed lead shield requiring clean smooth surfaces. A cleaning process of low-activity silica sand blasting and borated paraffin hot coating preservation was employed to guard against corrosion due to chemical and biological exposures. The resulting lead shield maintains low background contribution integrity while fully encapsulating the lead surface. We report the performance of the current LBC and a plan to develop a large germanium well detector for PMT screening. [Preview Abstract] |
Tuesday, April 8, 2014 1:54PM - 2:06PM |
Y13.00003: Performance of a Novel Gas Separation Research Column at Sanford Laboratory Angela Alanson Chiller, Christopher Chiller, Dongming Mei A world-wide rise in demand for ultrapure materials has necessitated innovation in the production of low impurity and isotopically separated materials that either has not been utilized in these new applications or relies on aging or energy intensive methods. These materials are sought after for large physics investigations, nuclear non-proliferation detection industries, medical imaging and new frontiers in electronic applications. Techniques in separating and purifying nuclear magnetic resonance isotopes of carbon, oxygen, xenon, krypton, and nitrogen are being developed at Sanford Laboratory, Lead, SD. A two-meter laboratory scale selective phase change column designed specifically for real-time sampling of the gas space at specific temperature and pressure is operated at gas/liquid and gas/solid equilibrium temperatures and pressures for selected gases. We report initial results and future applications. [Preview Abstract] |
Tuesday, April 8, 2014 2:06PM - 2:18PM |
Y13.00004: Development of Ge-based Detectors with n/$\gamma $ Discrimination at 77 K for Dark Matter Searches Wenzhao Wei, Dongming Mei, Chao Zhang Low background germanium (Ge) crystal detectors are a well-accepted methodology in the searches for dark matter. In this work, we report a development of micro-strip planar detectors with an effective threshold lower than 100 eV. By measuring plasma time, such a new-type Ge-based detector is expected to have capability of discriminating nuclear recoils from electron recoils due to plasma time difference of these two classes of events. Because of the extreme low energy threshold and n/$\gamma$ discrimination, the proposed detector is anticipated to have great sensitivity in detecting low mass WIMPs and low-energy neutrino interactions. [Preview Abstract] |
Tuesday, April 8, 2014 2:18PM - 2:30PM |
Y13.00005: LUX Trigger System Mongkol Moongweluwan The Large Underground Liquid Xenon Detector (LUX) is a dual-phase xenon TPC, operating at the Sanford Underground Research Facility (Lead, SD) designed to search for WIMPs. The LUX trigger system can trigger on S1 pulses, S2 pulses, or S1 pulses followed by S2 pulses within a time window (set by the maximum electron drift time within the detector). In the first WIMPs search run, the trigger system was set to trigger on S2 pulses. The S2 pulse area is calculated in real time and a trigger is generated when S2 pulses with areas of 8 or more photoelectrons (phe) are detected in two or more trigger channels. The performance of the system during the run was monitored using information integrated into the data stream. The noise in the system was monitored continuously by measuring the trigger rate as function of trigger threshold. These two processes are carried out in parallel with the main operation of the system. We determined that the trigger efficiency from this run was \textgreater 95{\%} for pulses with areas larger than 100 phe, which is equivalent to 3-4 ionizing electrons extracted from the liquid surface. In this talk, we will discuss our experience with the system during the first WIMPs run, and the method used to determined the trigger efficiency. [Preview Abstract] |
Tuesday, April 8, 2014 2:30PM - 2:42PM |
Y13.00006: Response of the LUX Dark Matter Detector to Ultra-Low Energy Nuclear Recoils James Verbus The LUX dark matter search experiment is a two-phase xenon time projection chamber located at the 4850' level of the Sanford Underground Research Facility in Lead, SD. I will describe the techniques used to calibrate the detector response to nuclear recoils for the first WIMP search result announced in October 2013 and report on subsequent calibration campaigns. A novel nuclear recoil calibration technique pioneered by LUX will be discussed and I will present a recent analysis of ultra-low energy nuclear recoil data down to $\sim$1 keVnr obtained using this technique. Results from the calibrations will be compared to existing LXe nuclear recoil calibrations and theory. [Preview Abstract] |
Tuesday, April 8, 2014 2:42PM - 2:54PM |
Y13.00007: Low energy nuclear recoils study in noble liquids for low-mass WIMPs Lu Wang, Dongming Mei Detector response to low-energy nuclear recoils is critical to the detection of low-mass dark matter particles-WIMPs (Weakly interacting massive particles). Although the detector response to the processes of low-energy nuclear recoils is subtle and direct experimental calibration is rather difficult, many studies have been performed for noble liquids, NEST is a good example. However, the response of low-energy nuclear recoils, as a critical issue, needs more experimental data, in particular, with presence of electric field. We present a new design using time of flight to calibrate the large-volume xenon detector, such as LUX-Zeplin (LZ) and Xenon1T, energy scale for low-energy nuclear recoils. The calculation and physics models will be discussed based on the available data to predict the performance of the calibration device and set up criteria for the design of the device. A small test bench is built to verify the concepts at The University of South Dakota. [Preview Abstract] |
Tuesday, April 8, 2014 2:54PM - 3:06PM |
Y13.00008: Precision measurement of quenching factors for low-energy nuclear recoils at TUNL Grayson Rich, Phil Barbeau, Calvin Howell, Hugon Karwowski With detector technologies becoming increasingly sensitive to exotic events, a thorough understanding of signal yield as a function of deposited energy is required for appropriate interpretation of results from cutting edge detector systems. Elastic neutron scattering is a probe which has been used to mimic the nuclear recoils which may be produced in detection media by light-WIMP interactions or coherent neutrino-nucleus scattering (CNS). We have built at the Triangle Universities Nuclear Laboratory (TUNL) a facility which produces pulsed, collimated, low-energy, quasi-monoenergetic neutron beams using the ${}^7$Li(p,n) reaction, resulting in fluxes of $\sim 1$ neutrons / (s $\cdot$ cm${}^2$) at $\sim$90 cm from the neutron-production target. The first precision results from this facility are reported for ultra-low-energy recoils in NaI(Tl) and CsI(Na) and future plans are outlined, including measurements on candidate materials for a CNS detector that can potentially be fielded at the Spallation Neutron Source of Oak Ridge National Laboratory as a part the Coherent Scatter Initiative (CSI). We discuss the implications of new, precise measurements of quenching factors on neutrino detectors and on current- and next-generation light-WIMP searches, particularly the DAMA experiment. [Preview Abstract] |
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