Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session J10: Tonne Scale Neutrinoless Double Beta Decay R&D IV |
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Sponsoring Units: DNP DPF Chair: Jason Detwiler, University of Washington Room: Sheraton Governor's Square 12 |
Sunday, April 14, 2019 1:30PM - 1:42PM |
J10.00001: Single Barium Atom Imaging in Solid Xenon for Barium Tagging in 136-Xe Double Beta Decay Christopher R Chambers, David Fairbank, James Todd, William M Fairbank The identification, or “tagging”, of the 136-Ba daughter atom that results from double beta decay of 136-Xe provides a promising technique for the elimination of backgrounds in a future upgrade of the nEXO neutrinoless double beta decay experiment. The tagging scheme being developed in this work utilizes a cryogenic probe to trap the barium atom in solid xenon and extract it from the time projection chamber filled with liquid xenon. The barium atom is then tagged via fluorescence imaging in the solid xenon matrix. Individual barium atoms in single vacancy matrix sites, have been imaged and counted with high definition by scanning a focused laser across the solid xenon matrix deposited on a sapphire window. This is the first time single atoms have been imaged in solid noble element and represents significant progress towards a practical barium tagging technique for nEXO. |
Sunday, April 14, 2019 1:42PM - 1:54PM |
J10.00002: Barium Daughter Tagging Using Single Molecule Fluorescence Imaging Austin McDonald The existence of Majorana fermions is of great interest as it may be related to the asymmetry between matter and anti-matter particles in the universe. However, the search for them has proven to be a difficult one. Neutrino-less Double Beta decay (NLDB) offers a possible opportunity for direct observation of a Majorana fermion. A robust observation of neutrinoless double beta decay is considered the most promising method to determine the Majorana nature of the neutrino. The detection of the single barium ion produced as a result of the double beta decay of xenon 136 would enable a new class of ultra-low background neutrinoless double beta decay experiments, which the NEXT collaboration is working to achieve. We will present recent progress toward realization of a barium tagging scheme in high pressure xenon gas, including, ion mobility in high pressure gas, custom fluorophores for barium sensing, and a high pressure optical system. This R&D adapts techniques from biochemistry and microscopy to yield a novel technology with potential to enable background free, ton-scale neutrinoless double beta decay searches. |
Sunday, April 14, 2019 1:54PM - 2:06PM |
J10.00003: Performance Analysis and Operation of the EXO-200 Muon Veto System Mitchell Hughes The EXO-200 experiment implemented a single-phase time projection chamber (TPC) as the combined source and detector for a neutrinoless double-beta decay search in isotopically enriched $^{136}$Xe. Despite being emplaced roughly 655 m underground at the Waste Isolation Pilot Plant near Carlsbad, NM, atmospheric muons still represented a significant background. In order to tag incoming muons and prompt decays, a muon veto system comprising 29 large plastic scintillator panels surrounded the TPC cleanroom on four sides. Throughout the lifetime of EXO-200, the muon veto system was monitored continuously to ensure acceptable performance and deadtime contributions. These measures included semi-annual calibration campaigns using a sealed radioactive source, the fitting of Landau peaks in underground muon spectra, and a battery of studies on ROI background impact, trigger efficiency, and rate for each veto system channel. Methods and conclusions from these studies will be discussed. |
Sunday, April 14, 2019 2:06PM - 2:18PM |
J10.00004: Studies to improve the liquid argon veto in LEGEND Neil C McFadden Neutrinoless double beta decay is a hypothesized lepton-number-violating process in which two protons decay to two neutrons, producing two electrons but no electron neutrinos. The LEGEND collaboration will search for this decay using high purity germanium detectors enriched in 76Ge with the sensitivity goal of half-lifes in excess of 1028 yr. A staged approach is being proposed in which a phase-1 200 kg (L-200) 76Ge detector array will be instrumented, followed by a phase-2 at a ton scale (L-1000). To increase the light collection efficiency of the L-200 liquid argon veto, several possible germanium detector array geometries are being explored using simulated optical probability maps. These maps, created with Geant4, are used to calculate photon detection probability as a function of position. This talk will demonstrate the power of this tool. For L-1000, an even lower background index is desired. To reach this goal, xenon doped argon is being investigated at the University of New Mexico. By adding 10 ppm of xenon to argon, the scintillation light of argon is shifted from 128 nm to 175 nm. Argon is more transparent and most materials are more reflective at 175 nm. Thus xenon doped argon should yield more light than pure argon. The results of this xenon doping will be presented. |
Sunday, April 14, 2019 2:18PM - 2:30PM |
J10.00005: Development of a low-background structural active-veto scintillator for rare event physics Michael T Febbraro, Gabriela Ibarra, Brennan T Hackett, Bela Majorovits, Elena Sala, David C Radford The polyester poly(ethylene 2,6-naphthalate) (PEN) is an attractive candidate as a 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. Recent formulations have been developed which greatly improve optical clarity, reducing radio impurities, and aiding in production of complex geometries. In this presentation, we will provide an update on synthesis, characterization, and potential applications of PEN and PEN derivatives for rare event physics experiments. Examples will be provided on applications for future germanium-based ton-scale 0νββ experiments. |
Sunday, April 14, 2019 2:30PM - 2:42PM |
J10.00006: Status of Low Tc IrPt TES Light Detectors for CUPID Bradford C Welliver, Giovanni Benato, Clarence L Chang, Alexey Drobizhev, Brian K Fujikawa, Raul Hennings-Yeomans, Goran Tripun Karapetrov, Yury G Kolomensky, Laura Marini, Valentyn Novosad, John Pearson, Tomas Polakovic, Benjamin EL Schmidt, Vivek Singh, Sachinthya Wagaarachchi, Gensheng Wang, Volodymyr G Yefremenko, Jianjie Zhang The Cryogenic Underground Observatory for Rare Events (CUORE) is currently searching for lepton number violating physics at the Laboratori Nazionali del Gran Sasso (LNGS). CUORE consists of 988 TeO2 crystals (742 kg) operated as cryogenic bolometers using neutron-transmutation doped (NTD) Ge thermistors. CUORE is expected to achieve a sensitivity of T1/2 = 9x1025 years (90 % C.L.) to the 130Te 0νββ decay half-life after 5 years of operation, and has already approached the expected background goal of ~0.01 counts/(keV·kg·yr). The CUORE Upgrade with Particle ID (CUPID) experiment will improve upon the CUORE background by having stricter radio-purity requirements, improved screening, enhanced target masses, and will have event by event discrimination of α and β interactions in the crystal via the collection of both light and heat. In order to meet the timing and energy resolution requirements of CUPID, light detectors using low-Tc transition edge sensors (TES) are a promising technology to use. This talk will present the current status of R&D between UCB, LBNL, and ANL in developing an IrPt bi-layer TES for use as a light detector and discuss how these devices can be realized for use in CUPID. |
Sunday, April 14, 2019 2:42PM - 2:54PM |
J10.00007: Large Area SiPM Readout and Signal Processing for nEXO Jonathan Echevers nEXO is a proposed 5 tonne liquid xenon time projection chamber to search for neutrinoless double beta decay of 136Xe. The central detector will implement several improvements over the previous generation experiment, EXO-200. One such improvement is the usage of silicon photomultipliers (SiPMs) instead of avalanche photodiodes (APDs) as scintillation light detectors. In this presentation, I will discuss the electronics readout of large area FBK UV sensitive SiPMs at liquid xenon temperatures, the digital processing of SiPM waveforms, and some of the challenges that are common to large area readout. We tested the SiPMs in both parallel and series configurations and demonstrated that up to 6 cm2 of SiPMs can be read out by a single front end channel while maintaining nEXO requirements specified in the pre-conceptual report. |
Sunday, April 14, 2019 2:54PM - 3:06PM |
J10.00008: Light Detection with VUV-sensitive SIPMs in nEXO Ako Jamil nEXO is a 5 tonne liquid xenon time projection chamber planned to search for the neutrinoless double beta decay of 136Xe with a target half-life sensitivity of approximately 1028 years, which depends on good energy resolution. Efficient light detection is critical for achieving the desired energy resolution σ/Qββ of 1% or better. nEXO will use 4m2 of Silicon Photomultiplier (SiPM) for the detection of the 175 nm scintillation light of Xe. Recent measurements show promising results from FBK with photon detection efficiencies (PDE) exceeding well above 15%. In addition, the dark noise and the correlated avalanche rate meet our requirements. This talk will cover the light detection in nEXO, the most recent results from measurement of FBK SiPMs and the potential energy resolution that is achievable in the nEXO detector by using these SiPMs. |
Sunday, April 14, 2019 3:06PM - 3:18PM |
J10.00009: LIquid Xenon Optical Characterization (LIXO) Arun Kumar Soma The next generation of Enriched Xenon Observatory (nEXO) is ~5t liquid xenon experiment for studies of neutrinoless double beta decay of 136Xe. Liquid xenon (LXe) scintillates in vacuum ultraviolet region (VUV). nEXO plans to use SiPM as photon detectors. Not enough information is available about reflective properties of materials and photon detectors in VUV region, which complicates optimization of light collection and detection in nEXO. LIXO is a dedicated setup constructed at the University of Alabama aimed to measure reflectivity of active (SiPM) and passive samples (Teflon,PEEK) as a function of angle in LXe. The setup can also measure photon detection efficiency (PDE) of photon sensors as a function of angle in LXe. In LIXO, spontaneous nuclear fission of 252 Cf excites LXe to produce ~178 nm light. The light is incident onto the sample to be investigated. The reflected light is measured with SiPM's to obtain specular and diffused reflectivity. A dedicated SiPM is used to monitor light stability and to trigger on light flashes produced by spontaneous fission. Further details of the experimental setup, first preliminary results on reflectivity and PDE of SiPM’s from Hamamatsu and FBK will be presented. |
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