5" PMT Bases for S3 Counters

The general layout of the 5" bases is similar to that of the 2" bases described above. It consists of a front tubular housing and a rear tubular housing, both made out of aluminum. They join at a coupling nut, as shown in the schematic diagram of Figure 5.11. The actual base where the PMT, $\mu$-metal shield, and the electronic dynode amplification chain are located, is different. The corresponding middle section, incorporating the above components, is made out of a moulded structure used in both the 5" bases and the aerogel Cerenkov counters. The PMT socket is moulded integral to the section and it is also spring loaded. The collets are different, due to the size of the light guide, but the method of assembly is very similar to that of the 2" base.

Figure 5.11: The 5" PMT base used in S3 trigger scintillators.

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