Beam spot weigth

Versions

Please provide the used software versions.

FLUKA:4-4.1
Flair:3.3-1

Description

Dear FLUKA Experts,

Greetings to all of you. I am currently confronted with a shielding problem related to multi - beam point radiation and would like to seek your valuable advice. The problem is described as follows: in one input file, I have defined three beam target points using the SPECSOUR, SPOTBEAM, SPOTPOS and SPOTDIR cards. The energies and corresponding beam intensities of these three beams are different. How should I set the SPOTWEIGHT values so that the calculated results can be scaled to the actual dose equivalent generated by the three beams hitting the targets with only a single NORM coefficient?

At present, I take the beam intensity of Target Point 1 as the reference, setting its SPOTWEIGHT to 1, and the SPOTWEIGHT values of the other two target points to the ratios of their respective beam intensities to that of Target Point 1. Based on this setting, can I convert the calculated results to the actual values simply by multiplying them by the beam intensity of Target Point 1?

Furthermore, for the scenario involving multiple beam target points, what value should the Sampling parameter in the SPECSOUR card be set to in order to yield results that are closer to the actual experimental outcomes?(Note: All the multiple beams exist simultaneously.)

Input files

Dear Yu Hua Fei,

thank you for your patience.

Your approach is correct, FLUKA will renormalize the weight of the spots.

To normalize the FLUKA score (in units of [1/part]) to physical results, you have to find the total intensity of the beams, i.e.
I_1 + I_2 + I_3 [part/s]
or
I_1 ( 1 + I_2/I_1 + I_3/I_1) [part/s]

therefore to normalize the FLUKA results you multiply by the intensity of beam 1 as well as the sum of the relative weights, i.e. the term in parenthesis above, which for you evaluates to 1.51.

For the sampling, the one that I recommend is random (<=0, e.g. put -1).

I hope this helps,

Stefano