Calculating the full-energy photopeak efficiency

Hello everybody.

I’m trying to help some colleagues transition from MCNP to FLUKA for the following case: calculating the full-energy photopeak efficiency (more details about what they are doing can be found in the article uploaded)

I received from them the input file (from MCNP) and imported it to FLUKA and with some small modifications/adjustments I managed to obtained a very nice geometry.

I have several problems and whilst I tried reading on the forum from previous posts I must admit that I am not quite sure that I understood what I have to do. To be totally honest I could say that I really did not understand much even though the explanations seemed quite clear and complete.

The first problem and the one with the least importance but there I really don’t know how to solve it is that when I have all the 12 detectors in the geometry I get the following errors while trying to run:
– Abort called from RPARSE reason NELEM=1, IMPOSSIBLE IC1!! Run stopped! STOP NELEM=1, IMPOSSIBLE IC1!!
– too many terms in parenthesis
I tried modifying the terms and seeing if I can improve the declaration but had no luck.

The second problem that I encountered is with the actual computation of the photopeak efficiency. As far as I understood from my colleagues in MCNP there’s an automatic function that does the Gaussian broadening of the spectrum and it is something quite simple. For FLUKA I understand from all that I have read here that that is something that one must do in post processing but I simply could not follow where and from where I should take my numbers.

What I was thinking of based of what my understanding is from reading on the forum is using the two cards that I read here can be used for this kind of problem: DETECT and EVENTBIN. From the DETECT I would get a nice spectrum and then I could calculate the photopeak by measuring the area under the peak of interest or by dividing the number of counts from the peak of interest to the total number of counts emitted from my source. Not quite sure though how can I get all that info from. EVENTBIN would be used for gathering information in terms of which event really took place in the active part of the detector?

I have attached the inputs and projects for two cases and also the article for my colleagues work:

-1st simulation 1DET consists of only 1 HPGE det (active part being C9901)
1DET.flair (4.9 KB)
1DET.inp (5.2 KB)

-2st simulation ALLDET consists of all 12 HPGE det (active part being C9901-C9912)
alldet.flair (35.5 KB)
alldet.inp (49.1 KB)

1-s2.0-S0168900210020279-main.pdf (376.6 KB)

Many many thanks in advance and sorry.

I know this was already discussed and explained but somehow I managed to wrap my head up in all the threads…

Best regards,
Irina

1. Converting from MCNP to FLUKA can lead to geometries with many parenthesis. FLUKA will try to expand them but in your case it fails. So, correctly you are enabling the online-evaluation of parenthesis with WHAT(1)=1 in GEOBEGIN.
I will try to upload in a while a short video on how you can try to expand and correct regions with parenthesis in flair (some times it works ok)

2. Indeed its very confusing this message: `RPARSE reason NELEM=1, IMPOSSIBLE IC1!! `
It happens during the parsing of the geometry, where there are some region expressions with lines containing only one | (bar).
If you concatenate the following line the error disappears, and your input runs happily
Find here the corrected input/flair
alldet.flair (35.4 KB)
alldet.inp (48.7 KB)

3. The DETGEB applies a Gaussian broadening

4. The EVENTBIN is a bit more complicated and requires that you create your processing program to analyze it

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Here is the short video, explaining one way how to correct parenthesis or overlaps

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Dear Vasilis,

Appologies for the late reply but I was kind of not around yesterday after I wrote on the forum. Unfortunately I don’t have access to my work computer during the weekend but many many thanks for your reply.

I think it really makes things a lot more clearer.

The explanation on the declaration of regions is quite helpful and the video that you made really got me to understand how to solve that if I encounter it again. Thank you so much for taking the time to do the video. That combined with the explanation from the first reply it’s extremely valuable information!

I will try and install fluka on my personal laptop and play with the DETGEB card and see what I can manage to to in order to get the results that they need. Most probably I will skip the EVENTBIN part for now as it seems to be a solution for someone with a bit more experience than myself. If I don’t manage to install it during the weekend first thing Monday morning I’ll do it at work and come back here.

Thank you again so much. You’ve been a huge huge help!

Have a great weekend.

Irina