The technique proposed for the Photon detectors is MWPC's with pad cathodes
covered with a CsI film, as developed by RD26. Being a member of the RD26
Collaboration [22],
Trieste has already started in 1995 some prototype work
and has taken up the responsibility for both the photon chambers and the
read-out electronics for both RICH1 and RICH2.
Figure 3.3:
Results of tests on the photon detector prototype, using a UV lamp
and a pad cathode plane without the CsI deposit:
a) Spectra of signal amplitude for single photon detection; the efficiency
for single photo-electron detection is 90% at 2100 V.
b) Distribution of the number of cathode pads giving signal above threshold
for single photon detection.
Figure 3.4:
Results of tests on the photon detector prototype, using a UV lamp
and a pad cathode plane with the CsI deposit:
a) Spectra of signal amplitude for single photon detection; the efficiency
for single photo-electron detection is 90% at 2050 V.
b) Distribution of the number of cathode pads giving signal above threshold
for single photon detection.
In the following we discuss separately: