Operation results are presented of a UV-sensitive gaseous photomultiplier (GPM) coupled through a MgF 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 gasflow mode with non-condensable gas mixtures. Gains of 10 4 were measured with a CsI-coated double-THGEM detector in Ne/CH 4 (95:5), Ne/CF 4 (95:5) and Ne/CH 4 /CF 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 4 (92.5:7.5) and a triple-structure THGEM/PIM/MICROMEGAS GPM in Ne/CH 4 (90:10) with a fast-current preamplifier.

Gaseous PhotoMultipliers (GPM) are a very promising alternative of vacuum PMTs especially for large-size noble-liquid detectors in the field of Functional Nuclear Medical Imaging and Direct Dark Matter Detection. We present recent characterization results of a Hybrid-GPM made of three Micropattern Gaseous Structures; a Thick Gaseous Electron Multiplier (THGEM), a Parallel Ionization Multiplier (PIM) and a MICROMesh GAseous Structure (MICROMEGAS), operating in Ne/CF 4 (90:10). Gain values close to 10 7 were recorded in this mixture, with 5.9keV x-rays at 1100 mbar, both at room temperature and at that of liquid xenon (T = 171K). The results are discussed in term of scintillation detection. While the present multiplier was investigated without photocathode, complementary results of photoextraction from CsI UVphotocathodes are presented in Ne/CH 4 (95:5) and CH 4 in cryogenic conditions.

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The properties of UV-photon imaging detectors consisting of CsI-coated THGEM electron multipliers are summarized. New results related to detection of Cherenkov light (RICH) and scintillation photons in noble liquid are presented.