Search

NEXT Collaboration: et al., Radio-frequency (RF) carpets with ultra-fine pitches are examined for ion transport in gases at atmospheric pressures and above. We develop new analytic and computational methods for modeling RF ion transport at densities where dynamics are strongly influenced by buffer gas collisions. An analytic description of levitating and sweeping forces from phased arrays is obtained, then thermodynamic and kinetic principles are used to calculate ion loss rates in the presence of collisions. This methodology is validated against detailed microscopic SIMION simulations. We then explore a parameter space of special interest for neutrinoless double beta decay experiments: transport of barium ions in xenon at pressures from 1 to 10 bar. Our computations account for molecular ion formation and pressure dependent mobility as well as finite temperature effects. We discuss the challenges associated with achieving suitable operating conditions, which lie beyond the capabilities of existing devices, using presently available or near-future manufacturing techniques., The University of Texas at Arlington NEXT group is supported by the Department of Energy, USA under Early Career Award number DE-SC0019054 (BJPJ), by Department of Energy, USA Award DE-SC0019223 (DRN), the National Science Foundation, USA under award number NSF CHE 2004111 (FWF), and the Robert A Welch Foundation, Y-2031-20200401 (FWF). The NEXT Collaboration acknowledges support from the following agencies and institutions: the European Research Council (ERC) under the Advanced Grant 339787-NEXT; the European Union’s Framework Programme for Research and Innovation Horizon 2020 (2014–2020) under the Grant Agreements No. 674896, 690575 and 740055; the Ministerio de Economía Competitividad and the Ministerio de Ciencia, Innovación Universidades of Spain under grants FIS2014-53371-C04, RTI2018-095979, the Severo Ochoa Program grants SEV-2014-0398 and CEX2018-000867-S, and the María de Maeztu Program MDM-2016-0692; from Fundacion Bancaria la Caixa (ID 100010434), grant code LCF/BQ/PI19/11690012; the Generalitat Valenciana of Spain under grants PROMETEO/2016/120 and SEJI/2017/011; the Portuguese FCT under project PTDC/FIS-NUC/2525/2014 and under projects UID/FIS/04559/2020 to fund the activities of LIBPhys-UC; the Pazy Foundation (Israel) under grants 877040 and 877041; the US Department of Energy under contracts number DE-AC02-06CH11357 (Argonne National Laboratory, USA), DE-AC02-07CH11359 (Fermi National Accelerator Laboratory), DE-FG02-13ER42020 (Texas A&M). DGD acknowledges support from the Ramón y Cajal program (Spain) under contract number RYC-2015-18820. JM-A acknowledges support from Fundación Bancaria la Caixa (ID 100010434), grant code LCF/BQ/PI19/11690012, and from the Plan GenT program of the Generalitat Valenciana , grant code CIDEGENT/2019/049.

Within the framework of xenon-based double beta decay experiments, we propose the possibility to improve the background rejection of an electroluminescent Time Projection Chamber (EL TPC) by reducing the diffusion of the drifting electrons while keeping nearly intact the energy resolution of a pure xenon EL TPC. Based on state-of-the-art microscopic simulations, a substantial addition of helium, around 10 or 15~\%, may reduce drastically the transverse diffusion down to 2.5~mm/$\sqrt{\mathrm{m}}$ from the 10.5~mm/$\sqrt{\mathrm{m}}$ of pure xenon. The longitudinal diffusion remains around 4~mm/$\sqrt{\mathrm{m}}$. Light production studies have been performed as well. They show that the relative variation in energy resolution introduced by such a change does not exceed a few percent, which leaves the energy resolution practically unchanged. The technical caveats of using photomultipliers close to an helium atmosphere are also discussed in detail., 8 pages, 7 figures

The search for neutrinoless double beta decay ( 0 ν β β ) is an important topic in contemporary physics with many active experiments. New projects are planning to use high-pressure xenon gas as both source and detection medium. The secondary scintillation processes available in noble gases permit large amplification with negligible statistical fluctuations, offering the prospect of energy resolution approaching the Fano factor limit. This Letter reports results for xenon secondary scintillation yield, at room temperature, as a function of electric field in the gas scintillation gap for pressures ranging from 2 to 10 bar. A Large Area Avalanche Photodiode (LAAPD) collected the VUV secondary scintillation produced in the gas. X-rays directly absorbed in the LAAPD are used as a reference for determining the number of charge carriers produced by the scintillation pulse and, hence, the number of photons impinging the LAAPD. The number of photons produced per drifting electron and per kilovolt, the so-called scintillation amplification parameter, displays a small increase with pressure, ranging from 141 ± 6 at 2 bar to 170 ± 10 at 8 bar. In our setup, this parameter does not increase above 8 bar due to non-negligible electron attachment. The results are in good agreement with those presented in the literature in the 1 to 3 bar range. The increase of the scintillation amplification parameter with pressure for high gas densities has been also observed in former work at cryogenic temperatures.

Performance characteristics are evaluated for a xenon driftless gas proportional scintillation counter (GPSC), for which detector pulses are formatted using very short shaping-time constants (~50 ns), and directly analyzed by the MCA without previous pulse time duration analysis and amplitude correction. The present detector and method allow the achievement of detector energy linearity and energy resolution similar to those of conventional GPSCs, reducing background levels and maximizing the detector count-rate capability. However, the obtained peak tails can be somewhat larger than those obtained with conventional GPSCs for X-ray energies above ~30 keV. Energy resolutions of 7.7%, 4.5% and 3.8% can be achieved for 5.9, 22.1 and 59.6 keV X-rays, respectively. http://www.sciencedirect.com/science/article/B6TJM-4BRJ561-J/1/7e1da2da1ab9696753720d39add33d51