I removed a scintillator from a uranium prospector’s scintillator [1] and pleased to find the MPT is a 1.5” D, 12 pin tube W/a 1.5 X 1’ xtal.
Using the catalog list for 1.5” MPTs, I found several 12 pin base diagrams all, IIRC, W/the same pins. The socket has three connections K, last dynode (#10) and the P (anode) The P was (is) isolated. So I connected it to the o’scope (W/a safety hV cap) in series) and the HV supply to the K and dynode 10.
At 1200V plenty of signal W/a Cs-137 several microCi source. BUT the signal positive!!!! After some cogitation, I realized that the P metal was allowing secondary emission. All my other sockets have the P connected to the HV. So any possible secondary emission is returned to the P. I suspect none possible, as the electrons have an ~ 200V hill to climb in addition to the fermi level depth.
Comments, anyone?
bc …. anthropomorphizes.
[1] the battery pack is more expensive than a used (eBay) HVPS! The prospector’s was purchased, and then given me back in ~ 1965.