Speaker
Description
In standard conditions, Xenon is the only gaseous element with a naturally occurring isotope undergoing double-beta decay. Hence exploiting a gaseous TPC as a tool for accurately reconstructing the topology of bb0nu events is very natural. When considering i) sensitivity to the lifetime of the decay and ii) energy resolution to separate it from regular bb2nu events, a high pressure electroluminescence TPC self-suggests. At the moment, the NEXT TPC is the most advanced implementation of this idea, relying deeply on common-wisdom assumptions like the monochromaticity of both primary and secondary scintillation (around 172nm), the lack of charge recombination for beta-events, or the validity of density-scalings for secondary scintillation. Looking into the future, the unambiguous elucidation of these phenomena becomes necessary in view of the upcoming ton and multi-ton scale experiments aimed at completely exploring the inverted hierarchy of neutrino masses.
Motivated by this, we conducted systematic measurements of S1 and S2
signals in a mini-TPC read out with wires, for varying pressures (1-10bar), pressure-reduced electric fields (0-100V/cm/bar) and wire voltages (up to 4kV). Systematic measurements of the time constants and scintillation yields obtained in these conditions will be presented, for alpha and beta sources in the VUV, UV and visible bands, and its impact on next generation xenon TPCs discussed.
