Reduce relative error

Dear Fluka Team,
I am facing an issue regarding relative errors.
I have calculated the energy deposited in TLDs (number of the tld used is 3) filled with Lithium Fluoride (LiF), the relative errors were less than 5% but when I switched the LiF material by AIR, the errors went up to 70% with the same variance reduction cards (e.g. EMFCUT in material and regions ) and tried to increase the number of primaries / cycles.
The geometry case is a simple one consisted of room (filled with AIR) with TLDs-Phantom system.
Please, any help would be appreciated

Dear @ibtissam.zidouh,

I would say that what you see makes sense. Air is less dense than a TLD, therefore less interactions occurs and so, it is more difficult to estimate the energy deposited and the relative errors are higher.

Dear @amario
I see what you mean, but I have to estimate the energy response dependence of dosimeters.
What I learned from published works is that the study is achieved by first, calculating energy deposited in LiF material and then in AIR occupied by TLDs.
I’d like to know, please, how could I achieve the calculations in AIR ? is there a way to force interactions in a volume or another way to estimate the required quantity ?

Thanks in advance

You might want to try to apply some biasing. Have a look at mean free path biasing from the biasing lecture of the Fluka course (slide 16 and following).

Thanks, I’ll try the biasing using the mean free path and I’ll get back to you .

Dear @amario
I tried the LAM-BIAS card with the SDUM=GDECAY for two different values of LAMBDA.
. B


But unfortunately the relative error still high .
Please could you help me solve this issue.

Dear @ibtissam.zidouh,
LAM-BIAS with SDUM=GDECAY is going to affect lifetime and decay length. But this is not your case, you use LAM-BIAS with an empty SDUM in order to reduce the interaction length.

Dear @amario
I have tried The LAM-BIAS with an empty entry for SDUM :
but the error does not change.

Please could you help me find how to overcome the problem .

Can you please share your .flair file and the paper you want to reproduce?

Dear @amario

After reviewing with my advisor and redefining the objectives of my research work, it seems that the paper I was trying to reproduce is not really serving the purpose (« article 1 » attached, for your reference).

In the meantime, I have found an analytical method to estimate the energy deposition in air, which was the main object of my request to you, and this actually solves the issue (« article 2 » attached, for your reference).

Thank you so much for your advice and support.

Best regards
article 2.pdf (286.5 KB)
article 1.pdf (368.3 KB)