Position-Sensitive Gaseous Photomultipliers

Abstract

Advances in the technologies associated with position sensitive gaseous detectors especially featuring CsI as reflective photoconverters will be reviewed. These photodetectors represent the most effective solution for what concerns cost and performance in the case of large area Cherenkov imaging applications in relatively low rate (or low occupancy) high energy physics and astrophysics experiments. Moreover, they are the only choice when the Cherenkov detector is embedded in a magnetic field. Recently proposed single-photon MPGDs (Micro-Pattern-Gaseous Detectors) will be also discussed in view of the successful efforts so far made to extend their sensitivity to visible light. With some modifications, photosensitive gaseous detectors can also be used in the imaging of X-rays and particles.

Evaluation of high sensitivity flat-panel gaseous detectors of flames, sparks and smoke

“…As can be seen, depending on the specific design, the developed detectors have 10 2 ÷10 3 times larger sensitivity than the best commercial sensors. [6,[8][9][10] and confirmed by us [11]. Here we present the most important parameters, in particular relative sensitivity, whose method of measurement is explained in section 2.…”

“…Measurements with a calibration cell show that the photo-current reaches a plateau at T > 80 • C. The QE of EF in full absorption (the region of the saturated photocurrent) is 𝑄 sat ≈ 20% at 190 nm [6]. Vapor pressure of EF at 80 • C and 40 • C, are about 2 and 0.2 Torr, respectively.…”

“…In the past years, much experience has been gained using photosensitive gaseous detectors in high-energy physics experiments (see, for example, [3][4][5]). With the aim to export this expertise for purposes of environmental monitoring, a new concept for a flame sensor was then proposed: a proportional gaseous detector, operating in avalanche mode with a discharge quencher gas mixture (made of polyatomic and noble gases), combined with special high sensitivity UV photocathodes, either solid, like Caesium Iodide (CsI), or gaseous, like vapors of ethylferrocene (EF) or terakis(dimethylamino)ethylene (TMAE) [6].…”

“…Some results of previous studies in this field are found in refs. [6,[8][9][10][11]. In particular the sensitivity relative to a Class-1 detector for some prototypes, the temperature interval within each detector can operate with high sensitivity, as well as their ability to detect flames in direct sunlight conditions are reported in table 1.…”

“…Although in these tests the effect of suppressing photocathode efficiency at long wavelengths was observed, it was not exploited for light filtering. However, important conclusions can be driven from subsequent studies, performed by several groups [6]. One of them is that the most appropriate materials for the covering layer are alkali-halides and some photosensitive liquids, for example EF, where the transport of free electrons on a reasonably long distance is possible [24].…”