spenceraxani
commented
5 years ago Hi Rogério,
You should expect about 0.4Hz of that to be coming from the cosmic ray muons. The remaining triggers are actually due to radiogenic backgrounds, like gamma and beta decays in the material around you. 200 counts in a minute is pretty high, but perhaps you are measuring in an environment that actually has a rather high background. The highest I’ve seen was in an apartment in Stockholm where I found about 2.5Hz.
The THRESHOLD value is the trigger value on the ADC (it is trustable to about 1%). It can be converted to a SiPM pulse amplitude using the calibration. If, say, you have better scintillator than us, the pulses will on average be higher and more will pass the trigger.
My best guess for a high count rate would have been from the black tape, but it sounds like you replaced it. You could try a couple of measurements to see if things are behaving well.
- Build another detector to measure the coincidence rate (this is nearly independent of the background)
- Put the detector in a lead shield to see if the rate decreases to ~0.5Hz
- Try measuring somewhere else, depending on where you are, the background rate can change
Thanks,
Spencer
On Oct 16, 2018, at 8:26 PM, rogerio-acioli notifications@github.com wrote:
Hi, Last week I finished the construction of my first detector. Everything looks fine, but the counts are very high. By using a THRESHOULD of 50 I'm finding something about 200 counts per minute. I had to use 220 of THRESHOULD to find the expected counting of 0,5 per minute
I already polish heated the scintillator, changed the screws for something with a smaller head and recovered the package with a better quality black tape. Anyway, the counts still high. I'm working with +29.7V at the HV pin.
Is that value of THRESHOULD trustable to work? I'm grateful for any help with that issue!
Att. Rogério.
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rogerio-acioli
Hi, Last week I finished the construction of my first detector. Everything looks fine, but the counts are very high. By using a THRESHOULD of 50 I'm finding something about 200 counts per minute. I had to use 220 of THRESHOULD to find the expected counting of 0,5 per minute
I already polish heated the scintillator, changed the screws for something with a smaller head and recovered the package with a better quality black tape. Anyway, the counts still high. I'm working with +29.7V at the HV pin.
Is that value of THRESHOULD trustable to work? I'm grateful for any help with that issue!
Att. Rogério.