The mobility of alkaline earth ions, Mg+, Ca+, Sr+ and Ba+, in liquid xenon is measured for the first time. The mobility of Tl+ is also determined for comparison with a measurement by other ...researchers. The Atkins cluster model for positive ions in non-polar liquids, based on the electrostriction effect, gives general agreement with the magnitude of the mobility values. This is some evidence that the positive ions form a snowball rather than a bubble structure in liquid xenon. However, the temperature dependence of the mobility does not match well with the Atkins theory, so there are still open theoretical questions on the nature of the environment of alkaline earth ions in liquid xenon. The lower mobility of Mg+ and Ba+ may be explained by a better size match to interstitial and substitutional sites, respectively, in solid Xe. These measurements are motivated by the development of a new technique to search for neutrino masses through 0nubetabeta decay of 136Xe. A key component of one version of the proposed experiment is tagging of 136Ba+ daughter ions in liquid 136Xe by laser-induced fluorescence.
Results from a search for neutrinoless double-beta decay (0νββ) of ^{136}Xe are presented using the first year of data taken with the upgraded EXO-200 detector. Relative to previous searches by ...EXO-200, the energy resolution of the detector has been improved to σ/E=1.23%, the electric field in the drift region has been raised by 50%, and a system to suppress radon in the volume between the cryostat and lead shielding has been implemented. In addition, analysis techniques that improve topological discrimination between 0νββ and background events have been developed. Incorporating these hardware and analysis improvements, the median 90% confidence level 0νββ half-life sensitivity after combining with the full data set acquired before the upgrade has increased twofold to 3.7×10^{25} yr. No statistically significant evidence for 0νββ is observed, leading to a lower limit on the 0νββ half-life of 1.8×10^{25} yr at the 90% confidence level.
Mobility of thorium ions in liquid xenon Wamba, K.; Hall, C.; Breidenbach, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2005, Letnik:
555, Številka:
1
Journal Article
Recenzirano
We present a measurement of the
226
Th ion mobility in LXe at 163.0
K and 0.9
bar. The result obtained, 0.240
±
0.011 (stat)
±
0.011 (syst) cm
2
/(kV-s), is compared with a popular model of ion ...transport.
We apply deep neural networks (DNN) to data from the EXO-200 experiment. In the studied cases, the DNN is able to reconstruct the relevant parameters—total energy and position—directly from raw ...digitized waveforms, with minimal exceptions. For the first time, the developed algorithms are evaluated on real detector calibration data. The accuracy of reconstruction either reaches or exceeds what was achieved by the conventional approaches developed by EXO-200 over the course of the experiment. Most existing DNN approaches to event reconstruction and classification in particle physics are trained on Monte Carlo simulated events. Such algorithms are inherently limited by the accuracy of the simulation. We describe a unique approach that, in an experiment such as EXO-200, allows to successfully perform certain reconstruction and analysis tasks by training the network on waveforms from experimental data, either reducing or eliminating the reliance on the Monte Carlo.
Characterization of large area APDs for the EXO-200 detector Neilson, R.; LePort, F.; Pocar, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2009, Letnik:
608, Številka:
1
Journal Article
Recenzirano
Enriched Xenon Observatory (EXO)-200 uses 468 large area avalanche photodiodes (LAAPDs) for detection of scintillation light in an ultra-low-background liquid xenon (LXe) detector. We describe ...initial measurements of dark noise, gain and response to xenon scintillation light of LAAPDs at temperatures from room temperature to 169
K—the temperature of liquid xenon. We also describe the individual characterization of more than 800 LAAPDs for selective installation in the EXO-200 detector.
Cosmogenic backgrounds to 0νββ in EXO-200 Albert, J.B.; Auty, D.J.; Barbeau, P.S. ...
Journal of cosmology and astroparticle physics,
04/2016, Letnik:
2016, Številka:
4
Journal Article
Recenzirano
Odprti dostop
As neutrinoless double-beta decay experiments become more sensitive and intrinsic radioactivity in detector materials is reduced, previously minor contributions to the background must be understood ...and eliminated. With this in mind, cosmogenic backgrounds have been studied with the EXO-200 experiment. Using the EXO-200 TPC, the muon flux (through a flat horizontal surface) underground at the Waste Isolation Pilot Plant (WIPP) has been measured to be $Φ$ = 4.07±0.14 (sys)±0.03 (stat)×10-7 cm-2 s-1, with a vertical intensity of $I_v$ = 2.97+0.14-0.13 (sys) ± 0.02 (stat) × 10-7 cm-2 s-1 sr-1. Simulations of muon-induced backgrounds identified several potential cosmogenic radionuclides, though only 137Xe is a significant background for the 136Xe $0νββ$ search with EXO-200. Muon-induced neutron backgrounds were measured using $γ$-rays from neutron capture on the detector materials. This provided a measurement of 137Xe yield, and a test of the accuracy of the neutron production and transport simulations. The independently measured rates of 136Xe neutron capture and of 137Xe decay agree within uncertainties. Geant4 and FLUKA simulations were performed to estimate neutron capture rates, and these estimates agreed to within ~ 40% or better with measurements. The ability to identify 136Xe($n,γ$) events will allow for rejection of 137Xe backgrounds in future $0νββ$ analyses.
Abstract
A new search for two-neutrino double-beta (2νββ) decay of 136Xe to the
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
state of 136Ba is
yr using a total 136Xe exposure of 234.1 kg yr. No statistically significant evidence for 2νββ decay to the
state is observed, leading to a lower limit of
yr at 90% confidence level, improved by 70% relative to the current world's best constraint.
Abstract
A new search for two-neutrino double-beta (2
νββ
) decay of
136
Xe to the
excited state of
136
Ba 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 2
νββ
decay to the
state of
136
Ba is
yr using a total
136
Xe exposure of 234.1 kg yr. No statistically significant evidence for 2
νββ
decay to the
state is observed, leading to a lower limit of
yr at 90% confidence level, improved by 70% relative to the current world's best constraint.
The hyperfine structure and isotope shifts of the 3s{sup 2}3p{sup 2} {sup 3}P{sub 2}{yields}3s3p{sup 3} {sup 3}D{sub 3}{sup o} transition in silicon have been measured. The transition at 221.7 nm was ...studied by-laser induced fluorescence in an atomic Si beam. For {sup 29}Si, the hyperfine A constant for the 3s{sup 2}3p{sup 2} {sup 3}P{sub 2} level was determined to be -160.1{+-}1.3 MHz (1{sigma} error), and the A constant for the 3s3p{sup 3} {sup 3}D{sub 3}{sup o} level is -532.9{+-}0.6 MHz. The isotope shifts (relative to the abundant isotope {sup 28}Si) of the transition were determined to be 1753.3{+-}1.1 MHz for {sup 29}Si and 3359.9{+-}0.6 MHz for {sup 30}Si. This is an improvement by about two orders of magnitude over a previous isotope shift measurement. From these results we are able to predict the hyperfine structure and isotope shift of the radioactive {sup 31}Si atom, which is of interest in building a scalable quantum computer.
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