An homeopathic cure to pure Xenon large diffusion

Abstract

The NEXT neutrinoless double beta decay (β β 0ν) experiment will use a highpressure gas electroluminescence-based TPC to search for the decay of Xe-136. One of the main advantages of this technology is the possibility to reconstruct the topology of events with energies close to Q β β . The rejection potential associated to the topology reconstruction is limited by our capacity to properly reconstruct the original path of the electrons in the gas. This reconstruction is limited by different factors that include the geometry of the detector, the density of the sensors in the tracking plane and the separation among them, etc. Ultimately, the resolution is limited by the physics of electron diffusion in the gas. In this paper we present a series of molecular additives that can be used in Xenon gas at very low partial pressure to reduce both longitudinal and transverse diffusion. We will show the results of different Monte-Carlo simulations of electron transport in the gas mixtures from wich we have extracted the value of some important parameters like diffusion, drift velocity and light yields. These results show that there is a series of candidates that can reduce diffusion without affecting the energy resolution of the detector and they should be studied experimentally. A comparison with preliminary results from such an ongoing experimental effort is given.

Gaseous and dual-phase time projection chambers for imaging rare processes

“…The key aspect is the relatively short time constant of the triplet state of xenon (100 ns), compared to the excimer quenching rates at the concentrations of interest (0.01%-0.5%). With the help of simulations [129,442], a reduction of the transverse diffusion by a factor nearing four can be anticipated in conditions where the available scintillation (suppressed by a factor five at 10 bar) allows reconstruction of both primary and secondary scintillation, at sufficiently good energy resolution. Moreover, the situation can be interpreted through a fully microscopic simulation, that has been recently developed for the task [129] (Fig.…”

Microscopic simulation of xenon-based optical TPCs in the presence of molecular additives

“…The first attempt to include the presence of molecular additives enforced the introduction of 2 and 3-body molecular quenching rates, and some coarse prescription for the cascade, a pioneering work done by Escada et al in [24]. This spurred subsequent experimental work in [25], during which the limitations of the original simulation approach and the necessity of a more refined treatment started to become apparent. It is important to note that phenomenological models popularized for dark matter detectors, like NEST [26], can, according to the authors, compute the scintillation in noble gases too.…”

The NEXT experiment to search for the neutrinoless double beta decay of Xe-136

“…This diffussion, with an rms of 10 mm after 1 meter of drift, can be improved using gaseous mixtures to the level of 2-3 mm rms [8]. In parallel, improvements in the reconstruction of the energy deposition in the active volume and event selection are being developed [9].…”