Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session S10: Minisymposium: Low Radioactivity Background Techniques in Underground Experiments - IIMini-Symposium
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Sponsoring Units: DNP Chair: Jordan Myslik, LBNL Room: A216 |
Monday, April 16, 2018 1:30PM - 1:42PM |
S10.00001: The LZ Liquid Scintillator Screener Detector Scott Haselschwardt Surrounding the LUX-ZEPLIN (LZ) liquid xenon time projection chamber will be an outer detector consisting of 17 tonnes of linear alklylbenzene-based, gadolinium-loaded, liquid scintillator (LS). Achieving a low concentration of radioactive impurities in the LS is crucial for the performance of the outer detector. The LZ LS Screener is a small detector designed to characterize radioimpurities in the outer detector LS. I report on a campaign undertaken with the LS Screener in the low-background environment of the former LUX water shield in the Davis Laboratory at the Sanford Underground Research Facility. A variety of radioimpurities, including those in the the uranium and thorium chains, $^{40}\textrm{K}$, and $^{14}\textrm{C}$, have been measured in the scintillator through modeling of the collected pulse area spectra. The radiopurity levels measured in the LS Screener are comparable to those achieved in other tonne-scale LS detectors and imply that the outer detector will successfully carry out its goals for the LZ experiment. [Preview Abstract] |
Monday, April 16, 2018 1:42PM - 1:54PM |
S10.00002: Radiogenic Backgrounds in the LUX Xenon and Detector Components Kelsey Oliver Mallory The Large Underground Xenon (LUX) experiment recently completed its operations phase. Analysis of its data continues, with one area of focus being to search for signs of new physics at energies beyond the signal range of the spin-independent WIMP (weakly interacting massive particle) interaction. Accurate characterization of radiogenic backgrounds is essential for correct extraction of signals and optimization of detector sensitivity. In this talk, we present analyses of $\alpha$, $\beta$, and $\gamma$ backgrounds intrinsic to the liquid xenon that originate from the detector materials. With this work, we refine previous radio-contamination measurements, and attempt to better understand the spatial variation of specific isotopes. [Preview Abstract] |
Monday, April 16, 2018 1:54PM - 2:06PM |
S10.00003: The challenges of radon-generated Po-210 surface contamination removal Vincente Guiseppe, Franklin Adams, Cabot-Ann Christofferson The next generation low-background detectors operating deep underground aim for unprecedented low levels of radioactive backgrounds. The deposition and presence of radon progeny on detector surfaces and surrounding materials is an added source of energetic background events. In addition to limiting the detector material's radon exposure to reduce potential surface backgrounds, it is just as important to clean surfaces to remove inevitable contamination. Previous studies of radon progeny removal from metal surfaces have generally found that a form of chemical etching is effective at removing some of the progeny (Bi and Pb), however more aggressive techniques are often necessary to effectively remove the Po atoms. In the absence of a more aggressive technique, a significant fraction of the Po atoms are believed to either remain behind on the surface or redeposit from the etching solution back onto the surface. We explore the nature of aqueous Po ions, the oxidation state of Po necessary to keep Po in solution, and the role of chemical kinetics during the etching of contaminated Cu surfaces. We present our findings on the role of oxidation and kinetics in the preparation of a clean etching technique. [Preview Abstract] |
Monday, April 16, 2018 2:06PM - 2:18PM |
S10.00004: A low-background structural active-veto scintillator for rare event physics Michael Febbraro, David Radford, Elena Sala, Bela Majorovits, Oliver Schulz, Chris Brightwell, Yuri Efremenko, Daniel Muenstermann, Rastislav Hodak, Markus Stommel, Markus Pohl The polyester poly(ethylene 2,6-naphthalate) (PEN) has been identified as an attractive candidate low-background material for future rare event physics experiments. The polyester exhibits ideal mechanical, electrical, and scintillation properties permitting its use not only as an active shield but also a structural component with a yield strength higher than that of copper at cryogenic temperatures [Yano, 1995]. It has also been used as a low background material for preparation of electrical ribbon cables for cryogenic detector applications [Brofferio, 2013]. In presentation, we will provide an update on synthesis, characterization, and potential applications of PEN and PEN derivatives in rare event physics such as a future germanium-based ton-scale 0$\nu\beta\beta$ experiment. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy. [Yano, 1995] Yano O, et al., Prog Polym Sci (1995) [Brofferio, 2013] C. Brofferio, et al., NIMA 178 (2013) [Preview Abstract] |
Monday, April 16, 2018 2:18PM - 2:30PM |
S10.00005: Simulating Liquid Noble Gas Purity Monitors Philip Weigel, Erin Hansen, Michelle Dolinski Electron drift purity monitors are used to analyze the lifetimes of electrons in liquid noble gas detectors. A quantitative measure of electron lifetimes--and hence purity--is established by drifting a known number of free electrons through the liquid and collecting them on an anode. The work presented here is the development of simulations that provide information about electron drift times in noble gas purity monitors. In the case of xenon, the drift length of electrons is highly limited by cost of xenon. The addition of high voltage switching can be used to artificially increase the drift length of the chamber without increasing the required volume of xenon. These simulations provide a computational method for modeling the high voltage switching monitor and testing its ability to measure long electron lifetimes. [Preview Abstract] |
Monday, April 16, 2018 2:30PM - 2:42PM |
S10.00006: 150 mm Cryogenic Silicon Detector Testing and Development Nicholas Mast, Matthew Fritts, Allison Kennedy, Rupak Mahapatra, Vuk Mandic, Nader Mirabolfathi, Anthony Villano The Super Cryogenic Dark Matter Search (SuperCDMS) experiment at SNOLAB plans to deploy a payload comprised of 100 mm diameter, 33 mm thick germanium and silicon ionization and phonon detectors. In order to scale up the sensitive mass of future searches, larger individual detectors are being investigated. In this talk I will present the first results of testing two prototype 150 mm diameter silicon ionization detectors. The detectors are 25 mm and 33 mm thick with masses 1.7 and 2.2 times larger than those planned for use in the SuperCDMS SNOLAB experiment. These devices were operated with contact-free bias electrodes to minimize leakage currents which currently limit operation at high bias voltages. One detector was instrumented to read out ionization signals using a single contact-free readout electrode and the other with an array of electrodes patterned on the crystal surface. I will discuss measurements of charge collection efficiency and energy resolution as well as event reconstruction models in these devices. The results show promise for the use of both large volume silicon detectors and contact-free electrode arrangements for scaling up solid state cryogenic detector mass and bias voltage. [Preview Abstract] |
Monday, April 16, 2018 2:42PM - 2:54PM |
S10.00007: Abstract Withdrawn |
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