Study of the quantum efficiency of CsI photo-cathodes exposed to oxygen and water vapour

A.Di Mauro,P Martinengo,F Piuz,E Schyns,J Van Beelen,T.D Williams

doi:10.1016/s0168-9002(00)01307-3

Abstract

The operation of CsI photocathodes in gaseous detectors requires special attention to the purity of the applied gas mixtures. We have studied the influence of oxygen and water vapour contaminations on the performance of CsI photocathodes for the ALICE HMPID RICH prototype. Measurements were done through comparison of Cherenkov rings obtained from beam tests. Increased levels of oxygen and water vapour did not show any effect on the performance. The results of this study found a direct application in the way of storing CsI photocathodes over long periods and in particular in the shipment of the HMPID prototype from CERN to the STAR experiment at BNL.

Highlights

The High-Momentum Particle IDentification (HMPID) system of ALICE at LHC is based on a CsI-RICH detector, aiming at charged p/K/p identification in the 1.5–5 GeV/c momentum range [1]
The influence of the exposure to O2 and H2O was investigated in two ways: (1) under stagnant conditions, through increased levels of O2 and H2O due to outgassing from the surfaces of the PC container; (2) under gas flow, with large concentrations of O2 in the detector gas mixture
PC32 was put at an overpressure of 165 mbar to ensure no external contributions due to possible micro-leaks

Summary

Introduction

The High-Momentum Particle IDentification (HMPID) system of ALICE at LHC is based on a CsI-RICH detector, aiming at charged p/K/p identification in the 1.5–5 GeV/c momentum range [1]. The use of CsI photocathodes (PCs) in gaseous detectors requires special attention to the purity of the gas. The influence of the exposure to O2 and H2O was investigated in two ways: (1) under stagnant conditions, through increased levels of O2 and H2O due to outgassing from the surfaces of the PC container (vessel or chamber); (2) under gas flow, with large concentrations of O2 in the detector gas mixture.

Results

Conclusion