Dear Developer
I want to use the Fluka program to calculate the energy and angle distribution of protons bombarding lithium targets. The following code gives the code I calculated using the mcnp program. How do I use the fluka program to complete the calculation of F21, F31, and F41 cards ?

in FLUKA you score surface current with the USRBDX card.

For F21, in FLUKA you can set up angular binning directly on the card, but in solid angles not in degrees, relative to the surface normal vector.
For F31, you will have to create separate scoring for all segments.
For F41, you can set the energy binning on the card itself.

Dear David,
Thank you very much for your reply, F31 and F41 card calculation, I understand what you mean, F21 card implementation I still do not understand, the following is my Fluka program settings, I use 30 BIN successfully calculated the energy distribution, but I use 40 BIN calculation of angular distribution when there are some problems, only one data is not 0, other data is 0.

you only get result in only bin because you are scoring on the surface of a sphere, so the normal and the particle direction is almost parallel.

You need to score the on the surface between the TARGET and VOID, to get the angular distribution. You may need to separate the VOID into a â€śupstreamâ€ť and â€śdownstreamâ€ť section, and use separate scorings to distinguish between the neutrons going forward and the backscattered ones.

Thank you very much for your answer, probably because I just started using Fluka, so I don 't understand what you mean. If you can, can you help me to change the input card, so that I can understand, thank you very much.

Is the calculation result of this solid angle corresponding to the calculation result of the F31 card in mcnp ? Is the calculation result of the angle corresponding to the F21 card in the MCNP ?

I donâ€™t looked at the geometry segments you are using for F31, and it is not possible to reproduce the linear angular binning in degrees with the FLUKA scoring, like in F21.
FLUKA can calculate the angular dependency only with linear binning along the solid angle.