Single photon detection by gaseous counters: Status and perspectives

The development of gaseous detectors for single photon detection has been mainly triggered by the requirements of the Cherenkov imaging counters and three generation of detectors have been developed: the gaseous detector with converting vapors included in the gas atmosphere, the open geometry detectors with solid state CsI photocathodes, where no ion back flow limitation can be envisaged, and the MPGD-based detectors with solid state CsI photocathodes, where the reduction of the ion back flow can be effectively introduced. Moreover, this last photon detector concept can also provide fast response opening the way to high rate capability applications. The use in gaseous counters of solid state photoconverters in the visible range is desirable, even if challenging due to the fragility and chemical reactivity of the converters: nevertheless, it is being pursued. Nowadays, the use of gaseous photon detectors is not restricted to Cherenkov counters: they are proposed for cryogenic noble liquid detectors in rare-event experiments and they can detect the luminescent light produced in multiplication processes in gas in a variety of applications in science and beyond. A short historical overview is provided; the status and perspective of gaseous detectors of single photons are analyzed in detail, including application examples.