Operation of MHSP multipliers in high pressure noble-gas
We report on the performance of a Micro-Hole & Strip Plate (MHSP) electron multiplier operating in pure Xe, Kr, Ar and Ne at the pressure range of 1 to 6 bar and in Ar – Xe mixtures at pressures ranging from 1 to 7 bar. The maximal gains at 1 bar Xe and Kr are 5*104 and 105, respectively; they drop by about one order of magnitude at 2bar and by almost another order of magnitude at 5-6 bar; they reach gains of 500 and 4000 at 5 bar in Xe and Kr, respectively. In Ar, the gain varies very little with pressure, from 3*103 to 9*103; in Ne the maximum attainable gain, about 105, is pressure independent above 2 bar. The results are compared with that of single- and triple-GEM multipliers operated in similar conditions. Potential applications are in hard X-ray imaging and in cryogenic radiation detectors. In the Ar - Xe mixture no significant reduction of the maximum achievable gain was measured. Absolute gains of 1–4*103 were reached in Ar/50 mbar Xe over this pressure range from 1 to 7 bar. Energy resolutions between 14% and 16% were reached for 6 keV X-rays.