How to get full-energy-peak efficiency?

[shusheng (Qinqing)]

Dear FLUKA experts,
I simulate the full-energy-peak efficiency of HPGe for 133Ba. And I use EVENTBIN card and DETECT card to get the energy spectrum(as shown below), but it is different from what is detected in reality. In MCNP, we can use GEB card to get a energy spectrum which is close to real situation by broading the energy spectrum. In FLUKA, how to get a real energy spectrum?
Thanks in advance

[horvathd (Dávid Horváth)]

Dear @shusheng,

please take a look at this post:

Gaussian Energy Broadening

Hi @Alexy fluka doesn’t offer any such possibility built in. One obvious way will be to convolute the recorded spectrum with the Gaussian function which can be even as a function of the energy like in MCNP. Another option would be to implement it with user routines I presume you are using the DETECT card. The DETECT card accumulates the energy deposition inside the variables ACCUMP and ACCUMN found in the “detloc.inc” include file. What you can do is in the end of each primary event, and be…

Cheers,
David

[shusheng (Qinqing)]

Dear Dávid Horváth,
I have read this reply, and I am confused about some questions.

1. He mentioned 20 regions, how to use DETECT card to keep track that I have applied the smoothing? (What kind of function of DETECT card I need to use?)
   2.I find there is a few words about usreou.f in user manual, I don’t know the physical meaning of the variable ACCUMP and ACCUMN, can you tell me?
   3.In the post, I download the simple example, the author have applied a naive 1 MeV smoothing, but I still fell confused about how to modify the usreou.f to get the energy spectrum of 133Ba.
   Thanks in advance

[horvathd (Dávid Horváth)]

Dear @shusheng,

I updated the user routine applying the Gaussian broadening in FLUKA: usreou.f (2.4 KB)

This fixes some issues with the storing the status of the smoothing with the previous one. To make it work, a dummy DETECT scoring has to be added after all other DETECT cards.

It implements the energy dependent FWHM, (the same as the one used in MCNP’s GEB keyword)

FWHM = a + b \sqrt{E + c E^2}

where a, b and c are the detector dependent constants. The attached example applies an energy independent 50 keV smoothing to the scoring regions.

Plus to clarify:

1. The number 20 refers to the maximum number of the DETECT scoring in FLUKA. The previous user routine stored the status of the smoothing in the place of the last scoring, but there was an issue with this approach. The current routine uses the already mentioned dummy DETECT scoring.

2. ACCUMP stores the value of the total energy deposited in a single event in all scoring regions specified in a DETECT scoring, while ACCUMN stores the total energy deposited in a single event in all trigger regions (Regions specified with the minus sign). See: https://flukafiles.web.cern.ch/flukafiles/manual/DETECT.html

3. The a, b, and c parameters are not depend in the specific isotope, but rather on the HPGe detector itself. If you are modeling a real detector, then it is possible to measure / calculate it. See: https://www.hindawi.com/journals/jep/2014/623683/

Cheers,
David