Detector Resolution Estimation and Discrepancy

PRA, BeqMoni, Theremino, Fitzpeaks and beyond!
Post Reply
kotarak
Posts: 46
Joined: 07 May 2020, 05:46
Location: Brookfield, CT, USA
Contact:

Detector Resolution Estimation and Discrepancy

Post by kotarak » 23 Mar 2021, 06:47

Hey guys,
I am testing a new NaI(Tl) with Cs-137 and I noticed a difference in the reported resolution between PRA and Theremino MCA.
In PRA when I mark the entire peak as ROI, (from the energy, just before it begins to raise to the energy when it pretty much levels with the background) it shows a resolution of 6.7%.
In theremino MCA, If I click on the center of the peak, then right-click on the line to engage the auto-FWHM estimation, the displayed resolution is 7.8%.
Which application is more trust-worthy? Am I doing something wrong?

Best,
Andrey
Andrey E. Stoev
Brookfield, Connecticut, USA

User avatar
Sesselmann
Posts: 845
Joined: 27 Apr 2015, 11:40
Location: Sydney
Contact:

Re: Detector Resolution Estimation and Discrepancy

Post by Sesselmann » 23 Mar 2021, 07:35

Andrey,

The two programs use a very different methods to discriminate pulses, so it is possible that they both calculate resolution correctly .

You are using a software MCA, so even though both programs receive the same digital waveform, they measure and calculate the wave height differently. First they have to establish a baseline and then capture the pulse before filtering out or discarding any badly formed pulses (pile up).

When the settings are optimal I suspect both methods will be similar.

Steven

kotarak
Posts: 46
Joined: 07 May 2020, 05:46
Location: Brookfield, CT, USA
Contact:

Re: Detector Resolution Estimation and Discrepancy

Post by kotarak » 23 Mar 2021, 09:49

Steven,
So is it a fair statement to say that peak evaluation for FWHM is the same on both applications, but the method used to build the spectrum is different, thus the plots are different and this results in a 1+% difference in the estimated resolution?
Obviously, the true resolution is X and one of the applications is closer to this value than the other.
1% is a significant resolution difference and I am just trying to figure out what is the actual resolution - is it 6.7% as PRA reports or is it 7.8% as according to Theremino MCA.
Perhaps I need to try a third application and hopefully I'll get 2 vs. 1.
I wonder if others experienced similar difference?

Best,
Andrey
Andrey E. Stoev
Brookfield, Connecticut, USA

User avatar
GigaBecquerel
Posts: 122
Joined: 04 Jul 2020, 07:34
Contact:

Re: Detector Resolution Estimation and Discrepancy

Post by GigaBecquerel » 23 Mar 2021, 19:23

Hello Andrey,

I personally would trust BecqMoni a lot more than theremino. Thereminos throws away a lot of spectroscopic information, and I generally got worse rez, both in numbers, as well as in actual peak separation.
You can guesstimate your resolution by how well the 4 peaks from 186 to 351 keV separate inthe Ra226 spectrum, that gives you a sanity check. At 6.0% they basically go down to the "baseline", and do not overlap.
Also, try importing your spectra into interspec and read resolution there. While this will most likely give you a third number it is a good constant, and lets you compare between different MCAs / Programs.

User avatar
Sesselmann
Posts: 845
Joined: 27 Apr 2015, 11:40
Location: Sydney
Contact:

Re: Detector Resolution Estimation and Discrepancy

Post by Sesselmann » 24 Mar 2021, 07:29

Andrey,

Download Interspec and do a comparison between PRA and Theremino.

https://www.gammaspectacular.com/blue/s ... c-software

Interspec only imports text files so you need to record the spectra in PRA or Theremino, then export the spectrum as a text file.

This will define which of the two software do a better job.

Steven

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests