Total posts : 45366
Carl, the only radon detector for home use I know of is an activated charcoal canister which is placed in a specified area for a specified time and then sent to a lab for analysis. The key to getting a meaningful radon reading is to separate the radon effects in the canister from other effects. This is done with a radiation mass spectrometer which detects and identifies the decay products from the radon. This is way beyond what I can do here.
I do plan to try to design and construct a multichannel analyzer which generates a histogram of the number of counts vs the energy. The voltage output from the photomultiplier tube in the scintillation counter is related to the energy of the radiation particle which causes the scintillation in the NaI:Tl crystal in the probe. I have the hardware and software to measure the voltage but the problem is that the pulses are 200 nanoseconds wide with amplitudes from tens of millivolts to 6 volts. The hardware and software is just not fast enough to capture these accurately. Very high speed analog circuitry is needed to pre-process the signal for computer sampling. The most easily workable scheme I have come up with is to construct a discriminator using a dual comparator with a discrimination window set and varied by the computer and the event stored in a flip-flop. This removes the real time constraint of the software. Even with missed events due to refractory time of the device, over time those captured will average out to give a good histogram showing the relative energies present. The actual counts will not be accurate but the relative counts in each energy slot should be. A flash A/D converter could work better but it is more complex
A geiger counter operating in the tube “geiger’ region as is customary cannot discriminate the energy since the amplitudes are all the same.
Yep, there has been severe thread drift from the topic of prototyping but I don’t mind sharing the technology beyond building. I see this type of activity as exercise for my brain.