Theremino MCA or Beqmoni ?

PRA, BeqMoni, Theremino, Fitzpeaks and beyond!
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Re: Theremino MCA or Beqmoni ?

Post by Sebastien_billard » 11 Feb 2019, 20:43

What do you find so desirable in PRA exactly ? I agree it seems to have a powerful pulse analysis engine, but it lacks feature to read the spectrum. Why no possibility to have a library of photopeaks or regions of interest ?
Sébastien Billard, north of France

25*25mm NaI detector

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Re: Theremino MCA or Beqmoni ?

Post by Sesselmann » 12 Feb 2019, 09:02


PRA was designed for the purpose of teaching University physics students about spectrometry, so many things that could have been automated have deliberately been left as manual processes.

Students were encouraged to analyse spectra, calculate energies and determine isotopes, rather than using a "no brain required" system that does all the work for them.

Of course when you understand the method you are qualified to move on and use any system.


Conor Whyte
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Re: Theremino MCA or Beqmoni ?

Post by Conor Whyte » 30 Jun 2019, 15:28

Actually I used PRA to do this back in the beginning of May / late April to teach an IB Physics 12 class basic Gamma Spectroscopy. I had a bunch of labeled isotopes (labels covered so no cheating) and some unknowns High value points scattered around the campus.
The students had to use survey meters to find the "hot" items (they were marked) but hidden (scavenger hunt) and bring back to the lab for analysis. The winners had to get the each of the isotope peaks correct and correctly ID the isotope. Winning teams got arduino uno boards to take home.

It was quite fun.

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Re: Theremino MCA or Beqmoni (and some questions)

Post by ColoRad-o » 15 Dec 2019, 07:51

Hello everyone!

I am now fairly familiar with PRA and I love the fact that it can save the “state” of a measurement. This permits one to go back with different or better calibration points and translate from “au” into keV. As suggested by Marek Dolleiser, it is useful to decompose the impact of ranges of pulse widths on the measured spectrum (done in an attached graphic). I love it to pieces.

On the other hand, the ability to examine pulses with Theremino MCA (henceforth ThMCA) is very attractive, but it leaves no careful trail to follow later, only some semblance of a calibrated spectrum. I have the sneaking suspicion (given the annotations and little blue boxes evident in ThMCA) that the pulse detection algorithm it uses is even more sophisticated than that in PRA, but if one cannot reliably save the complete measurement state or ingredients it is hard to make reproducible measurements (I suspect), so I use PRA almost all the time. It bugs me that if one naively starts a ThMCA count what appears is an allegedly “calibrated” spectrum with someone ELSE’s calibration—determined by whatever is in the Theremino_MCA_INI.txt file.
I have used the DAA (Digital audio analyzer) Theremino software to examine noise on USB ports, etc. Apart from the fact that the documentation (auto translated from Italian into English) is occasionally confusing, it looks very useful. To experts: I was puzzled about the 1 mVpp report (which I assume means that the white arrow marker in the middle of the screen shows about 1 mV peak to peak variation), which is well above what the Theremino folks suggest is adequate for USB port electrical nose. On the other hand, the noise spectrum (also attached) looks OK to me, but the Theremino documentation is a bit confusing right at this point. Do these look adequate to Theremino users?

I personally have no great need for a library of photopeaks since there are wonderful documents listing photopeaks from keV through MeV for radionuclides natural and artificial, with their relative intensities per decay.

A couple questions for experts on PRA and/or Theremino MCA

1. I can readily broaden the energy range using the sliders with ThMCA. Short of monkeying with the VOL on the GammaSpectacular box (which I would rather NOT do since there is no way to do this reproducibly [unlike the nice clear voltage readout on the box], is there an easy way to do this with PRA?

2. Is there a set of PRA settings which most people find are optimal for preparing gamma spectra? (I discovered some systematic shifts in changing the sampling rate from the minimal 48KHz to 384KHz sampling--see attached graphic.)

3. The phrase “arbitrary units” in PRA suggests that they can change arbitrarily from one measurement to the next. In my experience, they remain fairly fixed from one run to another. Can any one enlighten me about whether au are absolute or only reasonably constant? (Of course any change to hardware settings would shift everything, so I haven’t even played around with SHP or VOL settings on my GS-USB-PRO spiffy MCA enclosure (thank you Steven!). Formally, one should re-calibrate for each run, of course, but that’s a lot of exchanging of sources. I will report on the impact of shielding later.

4. I have been in the habit of reflexively “training” PRA before each run with 2,000-20,000 sample pulses via the Start Pulse Shape Acquisition mode and using the resulting pulse shape parameters. Is this a reliable procedure or is there something better (advanced pulse filtering?) to assure absolute comparability of runs taken at different times? [See the NEXT question.]

5. I have made long runs (20 million pulses) with low-level soil samples and also long runs with an empty sample chamber, in order to subtract background carefully. To my horror, at higher energies the “background” levels exceed somewhat those with a “live sample”. This makes background subtraction meaningless, of course. Do you all have suggestions for how to be systematic about measuring and subtracting background? It seems plausible to me that using exactly the same pulse shape parameters between the “live sample” and the “background” runs might help a lot.

I enclose some graphics which illustrate some of my points above. Perhaps the most generally useful to others is "spectrum by pulse width", in au.

This group is a WONDERFUL resource! Thanks to all.
A DAA noise measurement for an unplugged USB port
The noise spectrum of an unplugged USB port
Pulse width contains to measured gamma spectrum (au)
(316.87 KiB) Downloaded 205 times
Misbehavior of background vs live count
(286.49 KiB) Downloaded 210 times
Impact of low vs. high sampling rate
(308.68 KiB) Downloaded 221 times
D. M. Wood, retired physics professor
Arvada, Colorado (USA)
SAFECAST member (bGeigie Nano)

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