On the operation of a micropattern gaseous UV-photomultiplier in liquid-Xenon

Operation results are presented of a UV-sensitive gaseous photomultiplier (GPM) coupled through a MgF sub(2) window to a liquid-xenon scintillator. It consisted of a reflective CsI photocathode deposited on top of a THick Gaseous Electron Multiplier (THGEM); further multiplication stages were either a second THGEM or a Parallel Ionization Multiplier (PIM) followed by a MICROMEsh GAseous Structure (MICROMEGAS). The GPM operated in gas-flow mode with noncondensable gas mixtures. Gains of 10 sub(4) were measured with a CsI-coated double-THGEM detector in Ne/CH sub(4) (95:5), Ne/CF4 (95:5) and Ne/CH sub(4)/CF sub(4) (90:5:5), with soft X-rays at 173 K. Scintillation signals induced by alpha particles in liquid xenon were measured here for the first time with a double-THGEM GPM in He/CH sub(4) (92.5:7.5) and a triple-structure THGEM/PIM/MICROMEGAS GPM in Ne/CH sub(4) (90:10) with a fast-current preamplifier.