Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session PB: Mini-Symposium: Neutrinos and Nuclei XI: Double Beta Decay Hardware and Methods |
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Chair: Matthew Green, North Carolina State University Room: Statler |
Thursday, October 14, 2021 9:30AM - 9:42AM |
PB.00001: Study of PEN Scintillator Properties for Low-Background Applications in the LEGEND Experiment Brennan T Hackett In the era of ton-scale low-background experiments, there is an increasing necessity for low background active components capable of tracking residual radiation. The LEGEND Experiment (Large Enriched Germanium Neutrinoless Double Beta Decay Experiment is currently constructing its 200-kg phase and preparing a 1000-kg phase, which have background goals of 0.5 and 0.025 counts/ton/year/FWHM, respectively. One method to improve the background identification in LEGEND is to use active structural materials like PEN or poly(ethylene-2,6-naphthalate). PEN is of interest because of its robust structural characteristics and its scintillation light in the blue region as well as its wavelength shifting abilities. Luminescent and optical properties, including the quenching factor, surface reflectivity and attenuation length, have been measured in an effort to support utilizing this material in low background detectors. In addition, the radiopurity of PEN detector holders manufactured in a low-background environment has been measured using both ICP-MS and gamma-ray counting. Results and methods of these measurements will be presented. |
Thursday, October 14, 2021 9:42AM - 9:54AM |
PB.00002: The nEXO cryogenics and fluid handling and purification systems Andrea Pocar, Ethan C Brown The nEXO experiment will search for neutrinoless double beta decay in 136Xe, reaching a half life sensitivity beyond 1028 years. The experiment will consist of 5 tons of liquid Xe enriched to 90% in the isotope 136Xe, which will be used as both the decay source and detection medium. In order to reach the low background requirement, nEXO will utilize a dual fluid system based on the successful implementation in EXO-200. The liquid Xe is contained in a thin, high-purity copper vessel surrounded by a refrigerant, HFE-7000, to transfer the pressure to a dual walled carbon-composite cryostat. This allows isolation of the detector from radiogenic backgrounds with a minimum amount of material near the detector. The conceptual design of the fluid and cryogenic plants for the circulation, cooling, and pressure maintenance of the fluids, as well as the state-of-the-art, in-situ fabrication of the cryostats will be presented. |
Thursday, October 14, 2021 9:54AM - 10:06AM |
PB.00003: Development of a high-purity zirconium purifier for nEXO Clarke Hardy The nEXO experiment is a planned ton-scale liquid xenon time projection chamber (TPC) designed to search for neutrinoless double beta decay (0vBB) with a half-life sensitivity beyond 1028 years. To achieve optimal energy resolution, electronegative impurities that limit the electron lifetime must be removed from the xenon. Continuous purification of the xenon is one solution. While typical zirconium-alloy getter purifiers are well-suited to this purpose, they have been found to emanate radon, contributing to backgrounds which, in turn, reduce the sensitivity of the detector. This has motivated the development of a dedicated low-background purifier using high-purity zirconium. In this talk, the design considerations of such a purifier will be discussed and some preliminary results from a prototype will be presented. |
Thursday, October 14, 2021 10:06AM - 10:18AM |
PB.00004: Development of internal radioisotope calibration sources for the nEXO experiment Brian G Lenardo The nEXO experiment is a proposed next-generation search for the neutrinoless double beta decay (NDBD) of Xe-136. The primary detector will be a 5-ton, monolithic liquid xenon time projection chamber (TPC) with the source enriched to 90% in the isotope of interest. To optimize the energy resolution and event reconstruction, calibrations are needed to map the spatial- and time-dependence of the detector's response, particularly in the central regions of the detector. While the baseline design of nEXO uses gamma-emitting radiation sources deployed outside the TPC, the strong attenuation in liquid xenon motivates the development of radioisotopes which can be injected into the liquid xenon and dissolved throughout the detector. In this talk, I will describe recent simulations and experimental tests of two such sources, Rn220 and Xe127, which are being studied for use in nEXO. |
Thursday, October 14, 2021 10:18AM - 10:30AM |
PB.00005: Progress toward a multiplexed readout of transition-edge sensors for CUPID-1T Erin Hansen CUORE is an ongoing neutrinoless double-beta decay search using the isotope 130Te. The next generation detector, CUORE with Upgraded Particle IDentification (CUPID), will use scintillation light from Li2100MoO4 cryogenic calorimeters to tag particles by their heat-to-light signal ratio. CUPID is under development at the 250 kg level, but is looking to the next stage with 1 tonne of 100Mo (CUPID-1T). Scaling the next generation of crystalline detectors to this size requires ten thousand channels or more. Efforts to decrease wire density using frequency-division multiplexing are ongoing, and require technical solutions to demonstrate performance at operating temperature; systems must also adhere to stringent noise, crosstalk, and radiopurity constraints. We discuss a collaboration between UC Berkeley and Lawrence Berkeley National Laboratory toward these technical solutions. Multiplexing systems developed at LBNL and currently in use for cosmic microwave background experiments were adapted and implemented in a dilution refrigerator at UCB. Applications to research beyond NDBD (dark matter, coherent neutrino scattering, and next-generation quantum computing) are also considered. |
Thursday, October 14, 2021 10:30AM - 10:42AM |
PB.00006: Tagging Muon Induced Backgrounds in CUORE and CUPID Samantha Pagan CUPID, The CUORE Upgrade with Particle IDentification, is a proposed ton-scale search for neutrinoless double-beta decay located in Gran Sasso National Laboratory (LNGS). Building off the expertise and infrastructure of CUORE, the Cryogenic Underground Observatory for Rare Events, CUPID will improve discovery sensitivities by using an array of 100Mo scintillating bolometers. LNGS is located 1400 m underground, which provides 3400 m.w.e of overburden, reducing the muon rate in the CUPID detector by a factor of 106. Still, after planned upgrades such as particle identification, cosmogenic muons are projected to be CUPID’s most significant background, with ~2 muons/hour expected in the crystals. An active muon tagging system will mitigate this muon background. The system under development is a modular design of plastic scintillating panels with scintillating fiber, readout by SiPM detectors. The muon tagger must be highly compact to fit into the space constraints around the CUPID cryostat, and the tagger needs to be integrated into the CUPID DAQ and analysis framework. The progress towards designing this system with the highest efficiency, uniformity, and light collection within the constraints of CUPID will be discussed in this talk. |
Thursday, October 14, 2021 10:42AM - 10:54AM |
PB.00007: Detector response simulation for double beta studies Chiara Capelli The CUORE (Cryogenic Underground Observatory for Rare Events) experiment and its upgrade, CUPID (CUORE with Upgraded Particle IDentification), adopt the cryogenic calorimetric technique to search for neutrinoless double beta decay of 130Te and 100Mo, respectively. To discriminate the expected signal from other background sources, understanding the detector response to particle interactions is fundamental. For this purpose, the calorimeter response has been modeled and validated using CUORE signals. The superimposition of events close in time, referred to as pileup, is also modeled. In particular, the pileup of the two-neutrino double beta decay process is one of the main background sources for CUPID. In this talk, the framework and its application for waveform simulations and data analysis, enhanced by machine learning tools, will be shown. |
Thursday, October 14, 2021 10:54AM - 11:06AM |
PB.00008: Run Selection and Exposure Determination for the Majorana Demonstrator Thomas E Lannen The MAJORANA DEMONSTRATOR is an array of germanium detectors enriched in Ge-76 in order to search for neutrinoless double beta decay. The Demonstrator is surrounded by active and passive shielding operating in the Davis Campus on the 4850 ft level of the Sanford Underground Research Facility (SURF). Data taking with the enriched detectors ended in March 2021, while the array continues to operate with natural Ge detectors for background studies. Data produced by the MAJORANA DEMONSTRATOR is collected as runs up to 1 hour in length that are grouped together by run type and quality to form data sets for analysis. During the run selection process, an automatic run selection process examines each run against 15 quality attributes to provide a conservative ranking and create a good run list that defines the exposure available for analysis. An opportunity exists to revise the run selection criteria to potentially capture additional periods of time for usable data. This exercise will also inform data exclusion in future experiments. The run selection criteria and new exposure estimates for the full Majorana Demonstrator Ge-76 operational period will be presented. |
Thursday, October 14, 2021 11:06AM - 11:18AM |
PB.00009: Muon Analysis with the Majorana Demonstrator Franklin Adams The Majorana Demonstrator (MJD) is an array of germanium detectors surrounded by active and passive shielding operating in the Davis Campus on the 4850 ft level of the Sanford Underground Research Facility (SURF). The Demonstrator operated between 2015 and March 2021 with detectors enriched in Ge-76 to search for neutrinoless double-beta decay and now operates with natural detectors for background studies. Identification of the prompt cosmic muon background by the detector shielding is an important part of the overall background rejection strategy required by the search for neutrinoless double beta decay (0vBB). An array of scintillating panels surrounds the central detector to detect through-going muons. The four top panels and 12 bottom panels can be combined to form 144 muon hodoscopes that cover a range of incident muon angles. Accounting for the surface topology allows for the measurement of the muon intensity as a function of slant depth, spanning a water-equivalent depth of 4-7 km. The analysis of muon data from 2015-2021 will be presented. |
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