The Electronic Amplification Chain

The dynode amplification chain is mounted on a PC board, as is the case of the 2" base. A schematic diagram of the resistor chain is shown in Figure 5.12. As in the case of the 2" base, it incorporates an adjustable potentiometer (0-500 $\Omega$) and the nominal critical matching value is 90 $\Omega$. It has, in addition, a 51 $\Omega$ resistor in series with the 14th dynode, to further improve the shape of the anode pulse. A safe -HV to start with is -1.8 kV; it provides the best timing resolution with adequate pulse height for electrons during beam testing.

Figure 5.12: The 5" PMT base used in S3 trigger scintillators.

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