An introduction to BeqMoni - Karl B

Hi guys!

As you probably know, there are 3 major softwares for us to use; PRA, Theremino and BeqMoni. Each has its pros and cons, but personally I use BeqMoni 70% of the time, and PRA 30%. PRA is quick to setup and use, but often requires processing of the raw data if something else apart from a nice spectrum is needed. So, for those interested in performing quantification of isotopes in "real" (environmental and the like)BeqMoni is the way to go.

BeqMoni was finally translated into english a few months ago, but is still without an english manual. Many things are straightforward, others are not. This is not to be considered as a tutorial, but more as a "get started" guide.

Here we go!


Setting up your detector

Post: 278 - Karl B
April 17th, 2013 07:04:37pm
First, you must setup your detector. What I show here is how I set up my GS1100A, but the procedure will be similar for any GS model. The software should also work with any other detector drivers, and is said to work with external MCAs as well.

Go to "tools" --> "device configurations". If you have a GS1100A like I do, then you can start by cloning the "GX-2 / GS-1100A 44.1k v70" profile, and give it a suitable name (1).

2: Try these values initially, between 2500-3200 channels will probably be ok. The "channel pitch" function I can not say exactly how it works, but it controls in some way how the channels will be distributed in the available "space", which should be the amplitude range of the pulses (I might be wrong here). In any case, you can try to play with this and see what happens. Try values from 0.01 up to 0.04 ("standard") and slightly above. It does not take much here to change the spectrum quite a bit.

Important: If you modify the number of channels or the pitch, you have to redo the calibration. Also, if you want to compare spectra (or include a standard background) all these spectra must be collected using the same settings here, so fiddle around until you are satisfied and then leave these.



Detector specifics

Post: 279 - Karl B
April 17th, 2013 08:04:36pm
Now that you have a separate profile for the detector, it is time to let BeqMoni get to know it by acquiring pulses and learning the shape (just like in PRA; I believe it is based on Marek's method).

1: Select the appropriate audio input, sample rate and bit depth (try the ones in the picture)
I set the input level to 100, and thus controlled the volume from the windows audio device manager. Don't tick "auto", I got very strange results with this.

If one wants, (and uses BeqMoni alone) I guess it is possible to set the mic volume to 100% in windows, and then set the appropriate volume in BeqMoni for each detector. As I also use PRA, this would not be very good for me.

2: Not sure what these abbreviatons stand for, but I assume it has to do with the high/low threshold for the volume. I set these like this, and then played around with the below settings to see that I excluded the noise

3: Here it is some trial and error. Try modifying these settings until you have a complete pulse inside the window (you will see the pulse shape when you press "start"). Try the suggested settings and see what gives.

When you have settings giving you a nice pulse, let BeqMoni collect the 10000 pulses it wants (it will stop automatically) and then klick "save"

Now you should be ready to collect your first spectrum!



Energy calibration

Post: 280 - Karl B
April 17th, 2013 08:04:01pm
This window will allow you to use 1 (useless) 2 or 3 points for calibrating the energy axis of your detector. I strongly suggest you use the 3 points, and choose such calibration points that are; slightly below, in the middle of, and slightly above the energy range of which you are interested in.

Calibration using 3 points will also reveal the nonlinearity of your detector, as this will influence the quadratic term (x^2) of the calibration equation. If the detector's response is perfectly linear, this termi is "0" and cancels out, leaving only a y=kx+m linear equation.
If your detector has a very nonlinear response, try to lower the voltage on the driver a bit, and see if it helps. When you do this, you might have to increase the microphone volume.

To calibrate, acquire a spectrum (Cs 137 has two useful lines, but a Th-232/Ra-226 will be much more useful) until you have clear peaks. Go to the device manager, choose your device, and "energy calibration". Enter the peak energies that you want to use for calibration, and then use the "pick up" to mark those peaks in the spectrum. If you used 3 peaks for calibration, click "exec by 3" to calculate the calibration equation. Click save.

To have your spectrum updated with the calibration, make sure you have paused the acquisition. then click the round arrow next to the "device config" menu in the main window. This will update the spectrum with any changes done to the detector profile, such as calibration, # of channels, channel pitch and so on.

Now you can inspect the spectrum, and see how the calibration turned out. It is best if you calibrate your system when it is properly warmed up. Which peaks that are suitable for calibration will depend on your detector, source (and strength), acquisition time and so on.

In my case, 2 Thorium lantern mantles give an excellent spectrum for calibration within 15 minutes. If I want to endulge myself, I wait 30 minutes and ge a nice peak also at 2600 keV, giving me peaks from appr 50 up to 2600 keV to choose from for calibration. The Th-232 spectrum is also very rich in peaks and a real "benchmarker" for your detector, and the lantern mantles are only a few dollars on ebay, so it is really a "must-have" for hobby spectrometrists.

It is now late in Sweden... tomorrow I will post on the main window in BeqMoni, and the functions and features there.




The main window

Post: 281 - Karl B
April 18th, 2013 08:04:34pm
Now that you have setup your detector, you should see pulses coming in and the spectrum appearing.
I guess that you like me now are eager to click around like crazy in the interface. Please do.

When you have satisfied these urges, there are some features that I would like to highligt

1: Here you can select which (if you have more than one) detector you want to use for the acquisition. You can also choose the (set of) regios of interest (ROI) which is a neccesity to perform any kind of quantification into Bq of the detected isotopes. The default ROIs can be used as a guide to see how it works. You can clone these and use as a template for your own ROIs of choice.

Here you can also add a background spectrum which you have collected previously.
Otherwise this part is quite straightforward. A good hint is that if you perform calibration, you can then pause the acquisition and press the update button next to the detector dropdown list, and this will update the spectrum (consequently, you don't have to start a new spectrum)

2: Here you see the measurement results from you acquisition. If you have not chosen a ROI profile (see 1) you will not see anything here. For useful data here you need to define your ROIs based on you detectors resolution, and also calibrate against sources with known activity in a well-controlled geometry, so that a "Bq/cps" correction factor can be applied.

3: Here you can see the incoming pulses. This can be helpful to detect a saturated signal (the pulses "hit the roof"), which will also be visible as a sharp end of your spectrum. Lower your volume or the bias voltage and see if thing improve.

You can also modify the parameters of the "peak detection" function. You can also edit the nuclide definitions here, which are saved in the config\NuclideDefinition.xml file
This requires some playing around, as the resolution of your detector will influence the peak shape and thus how the peaks should be identified.

The tab "sample information" allows you to enter information about your samples. If you want to have the quantitive results in "Bq/kg" or "Bq/ml" you have to enter weight or volume here.

4: Here you can import other spectra for direct comparison within the same spectrum window.

5: This window displays information about the current location (or selection) of the mouse cursor. If you also loaded a background spectrum, you will get "net counts" and "net CPS"

6: You guessed it: The spectrum! The toolbar below allows you to change how the spectrum is displayed, turn on/off peak detection, and so on. You can also fine-tune the calibration here.

Now you should be well on your way to collect nice spectra also in BeqMoni!




Re: An introduction to BeqMoni

Post: 283 - Steven Sesselmann
April 19th, 2013 05:04:09am

Great effort, this will help a lot of users get started, I read through it quickly and could't see any major problems.

Just one question, does the quadratic factor in the energy calibration update automatically when you select three calibration points, or do you need to work it out?


Re: An introduction to BeqMoni

Post: 284 - Karl B
April 19th, 2013 07:04:50am
Thanks Steven!

The quadratic factor is calculated automatically if you choose 3 calibration points AND press the "exec by 3" button. I assume it will only calculate a straight line equation if you press "exec by 2" although you have entered 3 calibration points.

Here it is handy to pause the acquisition, (re)do the calibration, save the changes, and press the "update" button next to the detector dropdown menu. This will update the current spectrum, and there is no need to start a whole new spectrum in order for the changes to take effect (as I did at first, before realizing this)

If anyone has other ideas of how the calibration equation should be calculated, one can enter own values and use. However, I attempted several times to extract the channel number and use more than 3 calibration points in excel to make a calibration equation, but it does not work so well. Therefore I suspect BeqMoni does something more than just a simple linear-quadratic regression.

In any case, I usually get a very good calibration within BeqMoni.

Re: An introduction to BeqMoni

Post: 665 - Vsingh
February 5th, 2014 01:02:59pm
I am trying to replicate some of your interesting work. I have tried theramino and PRA. I would like to try Becqmoni but I can't seem to find a way to download it. The link on this site just puts me in Japanese nowhere land. Suggesstions ?

Re: An introduction to BeqMoni

Post: 666 - Karl B
February 6th, 2014 09:02:59am
Hi Vsingh! Go to this link The link can also be found here on "software downloads" and then choosing the Google translate link. The latest version (0.9981b) can be downloaded on the left of the page. Good luck!

Re: An introduction to BeqMoni

Post: 1323 - Luuk
September 26th, 2014 08:09:19am
Hi Karl,
Can you tell me how to adjust the lower limit of Becqmoni.
I have a cutoff at channal 25 but need to raise it a little, to reduce my noise.

Re: An introduction to BeqMoni

Post: 1325 - Karl B
September 29th, 2014 07:09:11pm
Hi Luuk!

Yes, as I mentioned in the email you have to set the LLD of the pulse shape "window" as low as you can without getting a distorted pulse shape.

I usually put the same values in both fields where the LLD and ULD can be entered, it has worked well.

I uncross the "auto volume setting" and use 100 as volume, and instead adjust the volume in the windows mixer...

What could be worth comparing is to try to use PRA to find the lowest pulse level that can be captured without getting noise from the PMT: Set the pulse height threshold to "0" and collect the spectrum for just a few seconds. Usually, a sharp peak quickly rizes to the far left, at around 0.2 A.U. if the PMT is of fairly low noise. More noisy PMTs might have this peak at 1 or more.

Then check when this peak disappears into the normal "noise" again, and that is your cutoff value to put into the "pulse height threshold". As of now, I am not sure if this value is the same that could work for BeqMonis LLD, but it could be worth to keep in mind.
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