Advances in gaseous photomultipliers

Abstract

We review latest progress in gaseous photomultipliers (GPM) combining solid photocathodes and various types of novel electron multipliers. Cascaded gaseous electron multipliers (GEM) coated with CsI photocathodes can efficiently replace UVsensitive wire chambers for single-photon recording in Cherenkov and other detectors. Other hole-multipliers with patterned electrodes (Micro-Hole and Strip Plates) and improved ion-blocking properties are discussed; these permit reducing considerably photon-and ion-induced secondary effects. Photon detectors with other electron-multiplier techniques are briefly described, among them GPMs based on Micromegas, capillary-plates, Thick-GEMs and resistive Thick GEMs. The two latter techniques, robust and economically produced, are particularly suited for large-area GPM applications, e.g. in RICH. Cascaded hole-multipliers with very high ion-blocking performance permitted the development and the first demonstration of DC-operated visible-sensitive gaseous photomultipliers with bialkali photocathodes and single-photon sensitivity. Recent progress is described in GPMs operated at cryogenic temperatures for rare-event noble-liquid detectors and medical imaging.

Position-Sensitive Gaseous Photomultipliers

“…Applications of PSGPMs were widely extended (see review paper [18]]) when solid photo cathodes, in particular made of CsI, were combined with another gas multiplication structure called -hole-type‖ [19][20][21]. In a few words, the modern hole-type detector is a dielectric sheet metalized on both sides in which an array of holes is created by a chemical etching technique or by mechanical drilling (see Fig.…”

“…During the last decade or so there have been a lot of efforts in the development of gaseous detectors sensitive to visible light (see review papers [33,34]. The experience of several groups have however shown that it is not an easy task to employ solid photocathodes sensitive to visible light (SbCs, GaAs/Cs or bialkaline) in an ordinary gas amplification structure, such as wire chambers or parallel-plate chambers (PPAC) [22,35] There are two main problems: 1) any tiny trace of impurities (for example, oxygen or water) cause degradation of the photocathode quantum efficiency due the photocathode destruction 2) in presence of high quantum efficiency photocathodes, it is almost impossible to reach gains above 10-100 due to the photon and ion feedback.…”

Doubly doped BaY2F8:Er,Nd VUV scintillator

“…These scintillators can be coupled with the detectors filled with photosensitive gases such as tetrakis dimethylamine ethylene (TMAE) or triethylamine (TEA) or to the other VUV-sensitive detectors for example a photomultiplier with CsI photocathode (Schotanus et al, 1989;Chechik and Breskin, 2008). One of the promising candidates for the VUV scintillators can be for example the Nd-doped LaF 3 or BaY 2 F 8 (BaYF).…”

Photon imaging using post-processed CMOS chips

“…ese can be used to create large area detectors. Breskin et al work on such detectors coupled to photocathodes to create large area detectors capable of detecting single photons [42,43,44]. Many more variants of GEM detectors exist.…”

“…e photosensitivity is obtained by coating the grid with a re ective CsI photocathode [112]. CsI is a very robust photocathode that has been used in combination with many gaseous photon detectors [44]. In [113] a Micromegas device with a single anode is coupled to a CsI re ective photocathode.…”