Many surplus scintillation probes have a single connector through which the PMT is fed with high voltage and the anode signal is output. However, this may require an external “Bias-T” (a high voltage / signal splitter) to connect the probe to a high-voltage power supply that is separate from the PMT amplifier/processor.
I recently built a Bias-T for my tiny Scionix scintillation probe. The probe contains a Hamamatsu R1635P 10 mm-diameter photomultiplier tube coupled to a small NaI(Tl) scintillation crystal. The probe also contains the dynode voltage-divider string, and connections are made through a tiny high-voltage locking coaxial connector.
I built the Bias-T inside a Pomona model 2392 aluminum enclosure with three BNC connectors. Inside the box, a 1 MOhm resistor is used to bias the PMT from the high-voltage input connector (this value is appropriate for my application, but you may require a different value, typically within the 100 kOhm to 10 MOhm range). The PMT’s anode signal is coupled to the signal-output BNC connector through a 0.001 uF @ 3 kV capacitor. The aluminum enclosure provides appropriate shielding against noise, protects the user from high voltage, and makes it easy to connect instrumentation by inserting it in-line with the scintillation processor’s input.
