Dear FLUKA experts ,I’m trying to design a MLFC and I meet a problem.I want to obtain the charge deposition of a 250MeV proton beam at different positions in pure copper. Therefore, I used a USEBIN card to calculate its proton flux within 5.5cm to 6.5cm, with a beam direction of 1000 bins. I will perform Gaussian fitting on the proton flux obtained by differencing, and then I want to verify the empirical formula below.

where the The first parameter is the standard deviation of Gaussian fitting when there is dispersion, the second parameter is the standard deviation of Gaussian fitting when there is dispersion, and the third parameter is the effect of momentum dispersion on the standard deviation, which can be calculated using 3.2 * dp/p * range.

I set the energy of the beam card in Flair to 250MeV, but I am not sure how to set Δ P. I tried the flat type and the Gaussian type, and tried multiplying by 2.355 and not multiplying by 2.355, respectively. In total, the sigma values fitted in four cases did not approach my momentum dispersion setting of 0.5% well after theoretical formula calculation. I want to know how to set it up Δ P.

Thank you very much.

Dear @Nicolas_Zhou,

This is described in the manual 7.22.3. BEAM — FLUKA Manual .

Have a look at it.

Thank you very much for your advice，I will take a look.