High Pressure Gas Xenon TPCs for Double Beta Decay Searches

Abstract

This article reviews the application of high pressure gas xenon (HPXe) time projection chambers to neutrinoless double beta decay experiments. First, the fundamentals of the technology and the historical development of the field are discussed. Then, the state of the art is presented, including the prospects for the next generation of experiments with masses in the ton scale. So far, HPXe detectors have operated at ambient temperature with pressures varying between 5 bar -St.Gotthard TPC [Iqbal et al., 1987]-and 20 bar -NEXT-DBDM prototype [Álvarez et al., 2012a]-. The NEXT-White detector [Monrabal et al ., 2018] is currently taking data at 10 bar. In practice, at standard temperature, the operational pressure for ton-scale detectors will be in the range 10 bar to 20 bar. Given the density of xenon gas at a pressure of 1 bar and 300 K temperature (5.761 kg m −3 ), a HPXe TPC of 10 m 3 operating at 10 bar would hold a target mass of near 600 kg ( 1.2 ton at 20 bar). The detector dimensions, while large (e.g. 3.2 m length by 3 m diameter) appear as technically feasible. On the other hand, the NEXT demonstrators (NEXT-DEMO, NEXT-DBDM and NEXT-White) have shown excellent energy resolution and a powerful topological signature in this pressure range.However, pressure can be traded with temperature, as illustrated in figure 1, which shows the four isochoric (constant density) curves corresponding to pressures of 5, 10, 15 and 20 bar (at a temperature of 20 • C). An interesting possibility would be cooling the detector to temperatures near the liquefaction Frontiers

Coherent elastic neutrino-nucleus scattering at the European Spallation Source

“…Right: Example of energy resolution obtained for 41.5 keV gammas [105]. The very small Fano factor in xenon gas, two orders of magnitude lower than for liquid xenon, allows for excellent energy resolution even in large-scale detectors [106].…”

Double beta decay experiments at Canfranc Underground Laboratory

“…23 in terms of the accumulated exposure. The NEXT-100 detector will reach a sensitivity to the neutrinoless DBD half-life of 1×10 26 years for an exposure of 500 kg•year [103]. Although this is the same sensitivity already achieved by KamLAND-Zen (described in Sec.…”

“…23 in terms of the accumulated exposure. The NEXT-100 detector will reach a sensitivity to the neutrinoless DBD half-life of 1×10 26 years for an exposure of 500 kg•year [103].…”

“…But energy resolution is much better in gas than in liquid, since, in its gaseous phase, xenon is characterized by a Fano factor lower than 1, meaning that the fluctuations in the ionization production are smaller than the ones due to pure Poisson statistics. The application of HPXe TPCs to neutrinoless DBD experiments is specifically reviewed in [103].…”

Cosmogenic Activation in Double Beta Decay Experiments

“…In the approach followed by the SuperNEMO project [140], the DBD source is a thin sheet external to the detector, consisting of gas detectors for tracking and scintillators as calorimeters; it follows the successful "Neutrino Ettore Majorana Observatory" (NEMO) experiment at the Modane Underground Laboratory, which has released results for several DBD emitters [141][142][143][144]. Another approach to develop tracking detectors for DBD is based on TPCs, in particular filled with xenon (either gas or liquid) to investigate 136 Xe [145,146]. Tracks are obtained from the ionization while the energy is deduced from scintillation.…”