Trends in the development of large area photon detectors for Cherenkov light imaging applications

Nappi, E.

doi:10.1016/s0168-9002(03)00757-5

Cited by 4 publications

(2 citation statements)

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“…CsI-THGEMs are currently considered for the upgrade of the RICH systems at the CERN-ALICE and -COMPASS experiments [10,11]. The reasons to replace the CsI-MWPCs [12] in these experiments are numerous: The CsI-MWPCs operate at relatively low gas gains (∼ 10 4 ), limited by avalanche photon-feedback. Furthermore, there is evidence that at high counting rates the MWPCs suffer from feedback-related discharges, followed by difficulties to restore the operating voltage,…”

Section: Introductionmentioning

confidence: 99%

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Further evaluation of a THGEM UV-photon detector for RICH – comparison with MWPC

et al. 2010

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The operation of single-, double-and triple-THGEM UV-detectors with reflective CsI photocathodes (CsI-THGEM) in Ne/CH 4 and Ne/CF 4 mixtures was investigated in view of their potential applications in RICH. The studies were carried out with UV, x-rays and βelectrons and focused on the maximum achievable gain, discharge probability, cathode excitation effects and long-term gain stability. Comparative studies under similar conditions were made in CH 4 , CF 4 and Ne/CF 4 , with a MWPC coupled to a reflective CsI photocathode (CsI-MWPC). It was found that at counting rates ≤ 10 Hz/mm 2 the maximum achievable gain of CsI-THGEMs is determined by the Raether limit; at counting rates > 10 Hz/mm 2 it dropped with rate. In all cases investigated the attainable CsI-THGEM gain was significantly higher than that of the CsI-MWPC, under similar conditions. Furthermore, the CsI-THGEM UV-detector suffered fewer cathode-excitation induced effects as compared to CsI-MWPC and had better stability at high counting rates. KEYWORDS: Micropattern gaseous detectors; Photon detectors for UV, visible and IR photons;Avalanche-induced secondary effects; Cherenkov detectors. 1. High gains (> 10 5 ) are reachable with single-or cascaded-THGEM electrodes in selected gases; mixtures of choice could be Ne with a small addition of quenchers (CH 4 , CF 4 ) [3,4]. Due to the exponential nature of single-photoelectron pulse-height distributions, and taking into account signal-over-threshold considerations, a high detector gain is an important factor in improving single-photon detection efficiency. 2. A THGEM can operate in poorly quenched gas mixtures as well as in gases emitting UV light (e.g. noble gases [5], CF 4 [6,4]). This permits conceiving windowless detectors (same detector and radiator gas, e.g. like in [7]), with simpler layout and larger Cherenkov-photon detection yields. 3. In intense-background environment, THGEMs can operate in the so-called "Hadron-Blind mode" with zero or reversed electric field above the photocathode [8]; this significantly reduces particle-induced ionization signals [7]. CsI-THGEMs are currently considered for the upgrade of the RICH systems at the 10]. The reasons to replace the CsI-MWPCs [11] in these experiments are numerous: The CsI-MWPCs operate at relatively low gas gains (~10 4 ), limited by avalanche photon-feedback. Furthermore, there is evidence that at high counting rates the MWPCs suffer from feedback-related discharges, followed by difficulties to restore the operating voltage, up to 1-day periods [12]. This could have resulted from a cathode excitation process [13], in which the surface is modified under discharge-induced ion bombardment, with

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Section: Introductionmentioning

confidence: 99%

“…Ion-induced photocathode degradation in the open-geometry of wire chambers, affecting the detector lifetime, would be strongly reduced in CsI-THGEMs, where only a small fraction of avalanche ions hit the photocathode. However, replacing the CsI-MWPC currently used in these and in other experiments [11] should be carefully assessed and validated.…”

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confidence: 99%