High Voltage Generator for Geiger Tubes
Output Voltage vs. Input, measured by me
version 1
GM tube СИ3-БГ (SI3-BG) may be is not suitable for measuring the background radiation.
This tube is not very sensitive, it counts less than 1 cpm without any radiation sources around ??!! (in my case HV=420V)
Just looking at the mechanical construction of the GM tube, you can tell that the tube has a questionable sensitivity. The ionizing particle needs to enter a volume of gas between the anode and cathode in order to cause a count. The glass body and the size of the tube is a tell tale sign. The "good" GM tubes usualy have mostly metal body which serves as cathode and the particles enter thru the cathode (like in the russian SBM-20) or thru a mica window (as in the LND712). The sensitivity is much greater when the GM tube has a large volume AND large area - like in the "pancake" style detector tube.
ОтговорИзтриванеJust for comparison - I have a Gamma-Scout detector with LND712 tube and it counts about 10 cpm when shielded with 50mm Pb + 3mm Al(counting mostly hard cosmic X-rays). It measured background of about 0.13 - 0.15 uSv at my location, unshielded (or ~15-20 cpm). The popular russian GMT-03/SBM-20 should have higher sensitivity as it presents larger surface area for the particles but it doesnt count Alpha particles because it detects only particles able to penetrate the metal cathode. Your HV source should work with other tubes with some tweaking as most operate around 400-500V range, just check the specified anode resistor.
73
de Andrey, AE1S