Electroluminescence TPCs at the thermal diffusion limit

Abstract

The NEXT experiment aims at searching for the hypothetical neutrinoless double-beta decay from the ${}^{136}$Xe isotope using a high-purity xenon TPC. Efficient discrimination of the events through pattern recognition of the topology of primary ionisation tracks is a major requirement for the experiment. However, it is limited by the diffusion of electrons. It is known that the addition of a small fraction of a molecular gas to xenon reduces electron diffusion. On the other hand, the electroluminescence (EL) yield drops and the achievable energy resolution may be compromised. We have studied the effect of adding several molecular gases to xenon (CO${}_2$, CH${}_4$ and CF${}_4$) on the EL yield and energy resolution obtained in a small prototype of driftless gas proportional scintillation counter. We have compared our results on the scintillation characteristics (EL yield and energy resolution) with a microscopic simulation, obtaining the diffusion coefficients in those conditions as well. Accordingly, electron diffusion may be reduced from about 10 mm/$\sqrt{\mathrm{m}}$ for pure xenon down to 2.5 mm/$\sqrt{\mathrm{m}}$ using additive concentrations of about 0.05%, 0.2% and 0.02% for CO${}_2$, CH${}_4$ and CF${}_4$, respectively. Our results show that CF${}_4$ admixtures present the highest EL yield in those conditions, but very poor energy resolution as a result of huge fluctuations observed in the EL formation. CH${}_4$ presents the best energy resolution despite the EL yield being the lowest. The results obtained with xenon admixtures are extrapolated to the operational conditions of the NEXT-100 TPC. CO${}_2$ and CH${}_4$ show potential as molecular additives in a large xenon TPC, CH${}_4$ showing the best performance and stability to be used in the NEXT-100 TPC, with an extrapolated energy resolution of 0.4% at 2.45 MeV for concentrations below 0.4%.

22 pages, 8 figures

References in corpus (8)

• Search for Majorana Neutrinos near the Inverted Mass Hierarchy Region with KamLAND-Zen
• Secondary Scintillation Yield in Pure Xenon
• An RF-only ion-funnel for extraction from high-pressure gases
• Primary and secondary scintillation measurements in a xenon Gas Proportional Scintillation Counter
• Microscopic simulation of xenon-based optical TPCs in the presence of molecular additives
• Micromegas operation in high pressure xenon: charge and scintillation readout
• An homeopathic cure to pure Xenon large diffusion
• Microbulk Micromegas for the search of 0$\nu \beta \beta$ of 136Xe in the PandaX-III experiment

Cited by in corpus (7)

• Electron Transport in Gaseous Detectors with a Python-based Monte Carlo Simulation Code
• Neutral Bremsstrahlung emission in xenon unveiled
• Electron Drift and Longitudinal Diffusion in High Pressure Xenon-Helium Gas Mixtures
• Mitigation of Backgrounds from Cosmogenic ${}^{137}$Xe in Xenon Gas Experiments using ${}^3$He Neutron Capture
• Double Beta Decay Experiments at Canfranc Underground Laboratory
• A journey to ITACA: Ion Tracking with Ammonium Cations Apparatus
• Neutral Bremsstrahlung in TPCs