The Enriched Xenon Observatory (EXO) will search for double beta decays of
136Xe. We report the results of a systematic study of trace concentrations of radioactive impurities in a wide range of raw ...materials and finished parts considered for use in the construction of EXO-200, the first stage of the EXO experimental program. Analysis techniques employed, and described here, include direct gamma counting, alpha counting, neutron activation analysis, and high-sensitivity mass spectrometry.
We report on a comparison between the theoretically predicted and experimentally measured spectra of the first-forbidden nonunique β-decay transition 137Xe(7/2−) → 137Cs(7/2+). The experimental data ...were acquired by the EXO-200 experiment during a deployment of an AmBe neutron source. The ultralow background environment of EXO-200, together with dedicated source deployment and analysis procedures, allowed for collection of a pure sample of the decays, with an estimated signal to background ratio of more than 99 to 1 in the energy range from 1075 to 4175 keV. In addition to providing a rare and accurate measurement of the first-forbidden nonunique β-decay shape, this work constitutes a novel test of the calculated electron spectral shapes in the context of the reactor antineutrino anomaly and spectral bump.
Understanding reflective properties of materials and photodetection efficiency (PDE) of photodetectors is important for optimizing energy resolution and sensitivity of the next generation ...neutrinoless double beta decay, direct detection dark matter, and neutrino oscillation experiments that will use noble liquid gases, such as nEXO, DARWIN, DarkSide-20k, and DUNE . Little information is currently available about reflectivity and PDE in liquid noble gases, because such measurements are difficult to conduct in a cryogenic environment and at short enough wavelengths. Here we report a measurement of specular reflectivity and relative PDE of Hamamatsu VUV4 silicon photomultipliers (SiPMs) with 50 μm micro-cells conducted with xenon scintillation light (∼175 nm) in liquid xenon. The specular reflectivity at 15ˆ incidence of three samples of VUV4 SiPMs is found to be 30.4±1.4%, 28.6±1.3%, and 28.0±1.3%, respectively. The PDE at normal incidence differs by ±8% (standard deviation) among the three devices. The angular dependence of the reflectivity and PDE was also measured for one of the SiPMs. Both the reflectivity and PDE decrease as the angle of incidence increases. This is the first measurement of an angular dependence of PDE and reflectivity of a SiPM in liquid xenon.
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•We present a new and simple design of an RF-only ion funnel.•Longitudinal ion transport is provided by the residual gas flow through the funnel thus no DC drag field is required.•The ...presented ion funnel allows for ion extraction from argon and xenon gas from up to 10bar to 10−3mbar in only one step with very high efficiency.•First experimental results of ion extraction from high-pressure noble gas have been performed and are compared with gas dynamic and ion trajectory calculations.
An RF ion-funnel technique has been developed to extract ions from a high-pressure (10bar) noble-gas environment into a vacuum (10−6mbar). Detailed simulations have been performed and a prototype has been developed for the purpose of extracting 136Ba ions from Xe gas with high efficiency. With this prototype, ions have been extracted for the first time from high-pressure xenon gas and argon gas. Systematic studies have been carried out and compared to simulations. This demonstration of extraction of ions, with mass comparable to that of the gas generating the high-pressure, has applications to Ba tagging from a Xe-gas time-projection chamber for double-beta decay, as well as to the general problem of recovering trace amounts of an ionized element in a heavy (m>40u) carrier gas.
Abstract
Generative Adversarial Networks trained on samples of
simulated or actual events have been proposed as a way of generating
large simulated datasets at a reduced computational cost. In this
...work, a novel approach to perform the simulation of photodetector
signals from the time projection chamber of the EXO-200 experiment
is demonstrated. The method is based on a Wasserstein Generative
Adversarial Network — a deep learning technique allowing for
implicit non-parametric estimation of the population distribution
for a given set of objects. Our network is trained on real
calibration data using raw scintillation waveforms as input. We find
that it is able to produce high-quality simulated waveforms an order
of magnitude faster than the traditional simulation approach and,
importantly, generalize from the training sample and discern salient
high-level features of the data. In particular, the network
correctly deduces position dependency of scintillation light
response in the detector and correctly recognizes dead photodetector
channels. The network output is then integrated into the EXO-200
analysis framework to show that the standard EXO-200 reconstruction
routine processes the simulated waveforms to produce energy
distributions comparable to that of real waveforms. Finally, the
remaining discrepancies and potential ways to improve the approach
further are highlighted.
Abstract
The EXO-200 experiment searched for neutrinoless double-beta decay of
136
Xe with a single-phase liquid xenon detector. It used an active mass of 110 kg of 80.6%-enriched liquid xenon in an ...ultra-low background time projection chamber with ionization and scintillation detection and readout. This paper describes the design and performance of the various support systems necessary for detector operation, including cryogenics, xenon handling, and controls. Novel features of the system were driven by the need to protect the thin-walled detector chamber containing the liquid xenon, to achieve high chemical purity of the Xe, and to maintain thermal uniformity across the detector.
Silicon photomultipliers are regarded as a very promising technology for next-generation, cutting-edge detectors for low-background experiments in particle physics. This work presents systematic ...reflectivity studies of Silicon Photomultipliers (SiPM) and other samples in liquid xenon at vacuum ultraviolet (VUV) wavelengths. A dedicated setup at the University of Münster has been used that allows to acquire angle-resolved reflection measurements of various samples immersed in liquid xenon with 0.45° angular resolution. Four samples are investigated in this work: one Hamamatsu VUV4 SiPM, one FBK VUV-HD SiPM, one FBK wafer sample and one Large-Area Avalanche Photodiode (LA-APD) from EXO-200. The reflectivity is determined to be 25–36 % at an angle of incidence of 20° for the four samples and increases to up to 65 % at 70° for the LA-APD and the FBK samples. The Hamamatsu VUV4 SiPM shows a decline with increasing angle of incidence. The reflectivity results will be incorporated in upcoming light response simulations of the nEXO detector.
We present a measurement of the left-right cross-section asymmetry ( A(LR)) for Z boson production by e(+)e(-) collisions. The measurement includes the final data taken with the SLD detector at the ...SLAC Linear Collider during the period 1996-1998. Using a sample of 383 487 Z decays collected during the 1996-1998 runs we measure the pole value of the asymmetry, A(0)(LR), to be 0.150 56+/-0.002 39 which is equivalent to an effective weak mixing angle of sin (2)straight theta(eff)(W) = 0.231 07+/-0.000 30. Our result for the complete 1992-1998 data set comprising approximately 537 000 Z decays is sin (2)straight theta(eff)(W) = 0.230 97+/-0.000 27.
A new search for two-neutrino double-beta (2νββ) decay of 136Xe to the $0_1^ + $ excited state of 136Ba is performed with the full EXO-200 dataset. A deep learning-based convolutional neural network ...is used to discriminate signal from background events. Signal detection efficiency is increased relative to previous searches by EXO-200 by more than a factor of two. With the addition of the Phase II dataset taken with an upgraded detector, the median 90% confidence level half-life sensitivity of 2νββ decay to the $0_1^ + $ state of 136Ba is $ 2.9 \times 10^{24} $ yr using a total 136Xe exposure of 234.1 kg yr. Furthermore, no statistically significant evidence for 2νββ decay to the $0_1^ + $ state is observed, leading to a lower limit of $ T^{2\nu}_{1/2}(0^+ \rightarrow 0^+_1) \gt 1.4\times10^{24} $ yr at 90% confidence level, improved by 70% relative to the current world's best constraint.
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