Question about the mechanism of USRBIN scoring

Dear FLUKA experts, I have a question about the USRBIN scoring mechanism

In my knowledge, in Monte Carlo, step of individual history can be truncated if the distance of region boundary is closer than sampled stepsize.
My question is, how does it work in the case of bin boundary in USRBIN detector? Whether step of history is truncated by USRBIN bin boundary or not?

From this topics,

I guess that the FLUKA code do not truncate history step in bin boundary, so step-shape artifact was arise.
Is this correct? I want to know clearly about the mechanism of USRBIN detector.

Thank you for your help.

Correct, the step is truncated on the region boundary.

No, it’s not, since the scoring mesh is not meant to change the particle history. Still, the scoring algorithm apportions among different bins according to the respective step fraction (see the manual, namely Note 14).

Not really. The step reduction should be obtained on physical ground by the reduction of the fraction of kinetic energy lost in a single step.

Dear Francesco,

Thanks a lot of detailed comments.

So, the single step size which can be tuned by STEPSIZE card must not be larger than the bin size.

Thanks again!

As earlier indicated in the topic you refer to, I’d rather recommend the use of FLUKAFIX.