toc1955's video: Gamma Spectrometer with Labview

Gamma Spectrometer Labview Controlled. (Adolf Cortel, January 2023) Some time ago (2011), before the Fukushima disaster, I described a gamma spectrometer (https://youtu.be/x4EygC4K2vA ) based on the peaks detection and measurement with a software (PRA) developed by Marek Dolleiser The spectra were very good for such a simple setup but the recording time was very long. Later, another software and circuits aimed mainly to amateur gamma spectroscopists have been developed by Theremino (https://www.theremino.com/en/blog/gamma-spectrometry) using the sound card of the computer to capture the signals. The hardware is about the same in all the systems: a crystal of an scintillator (usually NaI:Tl coupled to a photomultiplier), a HV power supply with very low rippling, a circuit to amplify and conditioning of the pulses coming from the photomultiplier and some way of capturing these signals and analyze them. I described in this video the use of Labview as the software to capture, treat and measure the pulses to get the gamma spectra. In the setup I have taken some ideas from Theremino designs, particularly a circuit to reduce the rippling of the HV power supply as well as the first stage to amplify the pulses. A word about the HV power supply: since the voltage of the output pulses depends strongly on the HV applied to the photomultiplier, the power supply must be very stable. The position of the peaks in the final gamma spectrum can change a lot with only a few volts of change in the voltage of the supply. Using Labview for capturing the signals has big advantages; besides how easily the spectra can be plotted : - the NI MyDAQ adquisition module can work at a rate up to 200 kS/s which allows a good definition of the signals after being conditioned (peaks rising in 25 micros, which corresponds to maximums after 5-6 points of measurement and whole signals lasting about 1 ms of (peak+tail). This allows a high rate of measurement with a low proportion of rejected signals. - The digital filters provided by Labview, basically band pass filters, are useful to remove residual rippling from the power supply. - There is no need of an elaborate conditioning of the signals. The tails of the signals can be ignored; only the height of the peaks above the baseline are be considered. There is no problem with signals overlapping tails since the height of each peak is measured relative to the baseline where it lies. If two peaks are too near they are discarded. Labview does all this very easily. Even with this simple setup the resolution is the one that can be expected from the NaI scintillator, about 9-10% In the video you'll see examples of spectra corresponding to Cs-137, uranium and thorium ores, trinitite, Co-60 and uranium glass. Regarding the music: I've Got It Bad And That Ain't Good, by Johnny Hodges and Billy Strayhorn - I have not the rights, and I have used it only for the educational purposes to which this video is aimed.