2" PMT Bases for S1 and S2 Trigger Counters

A schematic diagram of the 2" PMT Base is shown in Figure 5.9. The Base consists of three main components. These are the front tubular housing (06), which encloses the PMT, part of the scintillator counter's light guide (01), and the mu-metal shield (10). The actual base with the socket and the dynode chain is a separate part, actually an assembly of parts (09-19). The rear tubular housing (07) completes the assembly and encloses the dynode chain and wiring. The three main sections join at the coupling nut (14), which threads partly inside the front tubular housing, while the rear tubular housing threads on the remaining part. The PMT and the electronic amplification components are mounted on a P.C. board (15) which is enclosed in an aluminum Faraday cage. This assures rigidity and protection from stray RF fields. The mu-metal shield is at cathode potential to minimize the dark current due to capacitive discharge in the photo cathode glass window.

Figure 5.9: The 2" PMT base used in S1 and S2 trigger scintillators.

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