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Author: Subject: Gamma spectrometer software question (Theremino)

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[*] posted on 28-8-2021 at 08:30
Gamma spectrometer software question (Theremino)

Hey, i got some time ago a old gamma spectrometer wich come from Oakridge national laboratory apparently, problem is that i am not able to get a correct spectrum on my computer.

I tried on different sources and the result was always the same, a big spike at 200 kEV

I use a ludlum gamma scintillation probe running on 900V, if i am right it's a 44-2 model (the label is damaged)
The spectrometer by itself seem to work fine, the number of count on screen is accurate
For the software i use thermino on my new gaming computer, i think it could come from it cause i don't know if the sound card is good for that, my old computer gave the same result
I use the microphone input in theremino
On the other side i had to make a DIY connection by cutting the ludlum cable and adding a second BNC output so i can connect it to the spectrometer (wasn't able to find and adapter or an other cable online)

The sources i tested the counter on were Ra226, Cs137 and Am241

If anyone have an idea about how i could make it work it would be lovely to share

[Edited on 28-8-2021 by Ormarion]
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[*] posted on 26-9-2021 at 01:26

can you read the signal with an oscilloscope?
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[*] posted on 26-9-2021 at 06:09

Microphone inputs are not good for spectroscopy software, they tend to distort the signals to the point of making them useless. Use a line input instead.

Also try a better piece of software called PRA: It works for me much better than Theremino. It's tedious to setup correctly though. The Theremino software makes a great deal of guessing and simplifications which usually result in prettier pictures, but can degrade the data.

The best way to get the signal into a computer for analysis is to use an external USB sound card - not the cheap Chinese ones, but a high-end card that can do 96- or 192-kHz sampling. I use a Behringer UMC204. It's expensive but it works great.
Its smaller brother the UMC202 should work fine as well, and it;s cheaper - especially if you don't care about the extra audio inputs and MIDI features of the 204.

[Edited on 26-9-2021 by stamasd]

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