Studies of THGEM-based detector at low-pressure Hydrogen/Deuterium, for AT-TPC applications

We study the performance of single- and double- THick Gas Electron Multiplier (THGEM) detectors in pure Hydrogen (H₂) and Deuterium (D₂) at low pressures, in the range of 100–450 torr. The effect of the pressure on the maximum achievable gain, ion-back flow and long-term gain stability are investigated for single and double cascade detectors. In particular, it was found that maximum achievable gains above 10⁴, from single-photoelectrons avalanche, can be achieved for pressures of 200 torr and above; for lower pressure the gains are limited by avalanche-induced secondary effects to a values of around 10³. The results of this work are relevant in the field of avalanche mechanism in low-pressure, low-mass noble gases, in particular for applications of THGEM end-cap readout for active-target Time Projection Chambers (TPC) in the field of nuclear physics and nuclear astrophysics