Measurements of electron drift properties in liquid and gaseous xenon are reported. The electrons are generated by the photoelectric effect in a semi-transparent gold photocathode driven in ...transmission mode with a pulsed ultraviolet laser. The charges drift and diffuse in a small chamber at various electric fields and a fixed drift distance of 2.0 cm. At an electric field of 0.5 kV/cm, the measured drift velocities and corresponding temperature coefficients respectively are \(1.97 \pm 0.04\) mm/\(\mu\)s and \((-0.69\pm0.05)\)\%/K for liquid xenon, and \(1.42 \pm 0.03\) mm/\(\mu\)s and \((+0.11\pm0.01)\)\%/K for gaseous xenon at 1.5 bar. In addition, we measure longitudinal diffusion coefficients of \(25.7 \pm 4.6\) cm\(^2\)/s and \(149 \pm 23\) cm\(^2\)/s, for liquid and gas, respectively. The quantum efficiency of the gold photocathode is studied at the photon energy of 4.73 eV in liquid and gaseous xenon, and vacuum. These charge transport properties and the behavior of photocathodes in a xenon environment are important in designing and calibrating future large scale noble liquid detectors.
nEXO is a proposed experiment to search for the neutrino-less double beta decay (\(0\nu\beta\beta\)) of \(^{136}\)Xe in a tonne-scale liquid xenon time projection chamber (TPC). The nEXO TPC will be ...equipped with charge collection tiles to form the anode. In this work, the charge reconstruction performance of this anode design is studied with a dedicated simulation package. A multi-variate method and a deep neural network are developed to distinguish simulated \(0\nu\beta\beta\) signals from backgrounds arising from trace levels of natural radioactivity in the detector materials. These simulations indicate that the nEXO TPC with charge-collection tiles shows promising capability to discriminate the \(0\nu\beta\beta\) signal from backgrounds. The estimated half-life sensitivity for \(0\nu\beta\beta\) decay is improved by \(\sim\)20\(~(32)\%\) with the multi-variate~(deep neural network) methods considered here, relative to the sensitivity estimated in the nEXO pre-conceptual design report.
In this paper we report on the characterization of the Hamamatsu VUV4 (S/N: S13370-6152) Vacuum Ultra-Violet (VUV) sensitive Silicon Photo-Multipliers (SiPMs) as part of the development of a solution ...for the detection of liquid xenon scintillation light for the nEXO experiment. Various SiPM features, such as: dark noise, gain, correlated avalanches, direct crosstalk and Photon Detection Efficiency (PDE) were measured in a dedicated setup at TRIUMF. SiPMs were characterized in the range \(163 \text{ } \text{K} \leq \text{T}\leq 233 \text{ } \text{K}\). At an over voltage of \(3.1\pm0.2\) V and at \(\text{T}=163 \text{ }\text{K}\) we report a number of Correlated Avalanches (CAs) per pulse in the \(1 \upmu\text{s}\) interval following the trigger pulse of \(0.161\pm0.005\). At the same settings the Dark-Noise (DN) rate is \(0.137\pm0.002 \text{ Hz/mm}^{2}\). Both the number of CAs and the DN rate are within nEXO specifications. The PDE of the Hamamatsu VUV4 was measured for two different devices at \(\text{T}=233 \text{ }\text{K}\) for a mean wavelength of \(189\pm7\text{ nm}\). At \(3.6\pm0.2\) V and \(3.5\pm0.2\) V of over voltage we report a PDE of \(13.4\pm2.6\text{ }\%\) and \(11\pm2\%\), corresponding to a saturation PDE of \(14.8\pm2.8\text{ }\%\) and \(12.2\pm2.3\%\), respectively. Both values are well below the \(24\text{ }\%\) saturation PDE advertised by Hamamatsu. More generally, the second device tested at \(3.5\pm0.2\) V of over voltage is below the nEXO PDE requirement. The first one instead yields a PDE that is marginally close to meeting the nEXO specifications. This suggests that with modest improvements the Hamamatsu VUV4 MPPCs could be considered as an alternative to the FBK-LF SiPMs for the final design of the nEXO detector.
Future tonne-scale liquefied noble gas detectors depend on efficient light detection in the VUV range. In the past years Silicon Photomultipliers (SiPMs) have emerged as a valid alternative to ...standard photomultiplier tubes or large area avalanche photodiodes. The next generation double beta decay experiment, nEXO, with a 5 tonne liquid xenon time projection chamber, will use SiPMs for detecting the \(178\,\text{nm}\) xenon scintillation light, in order to achieve an energy resolution of \(\sigma / Q_{\beta\beta} = 1\, \%\). This paper presents recent measurements of the VUV-HD generation SiPMs from Fondazione Bruno Kessler in two complementary setups. It includes measurements of the photon detection efficiency with gaseous xenon scintillation light in a vacuum setup and dark measurements in a dry nitrogen gas setup. We report improved photon detection efficiency at \(175\,\text{nm}\) compared to previous generation devices, that would meet the criteria of nEXO. Furthermore, we present the projected nEXO detector light collection and energy resolution that could be achieved by using these SiPMs.
The search for neutrinoless double beta decay probes the fundamental properties of neutrinos, including whether or not the neutrino and antineutrino are distinct. Double beta detectors are large and ...expensive, so background reduction is essential for extracting the highest sensitivity. The identification, or 'tagging', of the \(^{136}\)Ba daughter atom from double beta decay of \(^{136}\)Xe provides a technique for eliminating backgrounds in the nEXO neutrinoless double beta decay experiment. The tagging scheme studied in this work utilizes a cryogenic probe to trap the barium atom in solid xenon, where the barium atom is tagged via fluorescence imaging in the solid xenon matrix. Here we demonstrate imaging and counting of individual atoms of barium in solid xenon by scanning a focused laser across a solid xenon matrix deposited on a sapphire window. When the laser sits on an individual atom, the fluorescence persists for \(\sim\)30~s before dropping abruptly to the background level, a clear confirmation of one-atom imaging. No barium fluorescence persists following evaporation of a barium deposit to a limit of \(\leq\)0.16\%. This is the first time that single atoms have been imaged in solid noble element. It establishes the basic principle of a barium tagging technique for nEXO.
The next-generation Enriched Xenon Observatory (nEXO) is a proposed experiment to search for neutrinoless double beta (\(0\nu\beta\beta\)) decay in \(^{136}\)Xe with a target half-life sensitivity of ...approximately \(10^{28}\) years using \(5\times10^3\) kg of isotopically enriched liquid-xenon in a time projection chamber. This improvement of two orders of magnitude in sensitivity over current limits is obtained by a significant increase of the \(^{136}\)Xe mass, the monolithic and homogeneous configuration of the active medium, and the multi-parameter measurements of the interactions enabled by the time projection chamber. The detector concept and anticipated performance are presented based upon demonstrated realizable background rates.
The central drift chamber for the MARK III detector at SPEAR
Nuclear instruments and methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment/Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/1984
Journal Article
We report on the performance of silicon photomultiplier (SiPM) light sensors operating in electric field strength up to 30 kV/cm and at a temperature of 149K, relative to their performance in the ...absence of an external electric field. The SiPM devices used in this study show stable gain, photon detection efficiency, and rates of correlated pulses, when exposed to external fields, within the estimated uncertainties. No observable physical damage to the bulk or surface of the devices was caused by the exposure.
nEXO Pre-Conceptual Design Report S Al Kharusi; Albert, J B; Alfaris, M ...
arXiv (Cornell University),
08/2018
Paper, Journal Article
Open access
The projected performance and detector configuration of nEXO are described in this pre-Conceptual Design Report (pCDR). nEXO is a tonne-scale neutrinoless double beta (\(0\nu\beta\beta\)) decay ...search in \(^{136}\)Xe, based on the ultra-low background liquid xenon technology validated by EXO-200. With \(\simeq\) 5000 kg of xenon enriched to 90% in the isotope 136, nEXO has a projected half-life sensitivity of approximately \(10^{28}\) years. This represents an improvement in sensitivity of about two orders of magnitude with respect to current results. Based on the experience gained from EXO-200 and the effectiveness of xenon purification techniques, we expect the background to be dominated by external sources of radiation. The sensitivity increase is, therefore, entirely derived from the increase of active mass in a monolithic and homogeneous detector, along with some technical advances perfected in the course of a dedicated R&D program. Hence the risk which is inherent to the construction of a large, ultra-low background detector is reduced, as the intrinsic radioactive contamination requirements are generally not beyond those demonstrated with the present generation \(0\nu\beta\beta\) decay experiments. Indeed, most of the required materials have been already assayed or reasonable estimates of their properties are at hand. The details described herein represent the base design of the detector configuration as of early 2018. Where potential design improvements are possible, alternatives are discussed. This design for nEXO presents a compelling path towards a next generation search for \(0\nu\beta\beta\), with a substantial possibility to discover physics beyond the Standard Model.
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