Neutron Energy in 10B(n, α) Reaction

Physics, Transport and Magnetic Fields
1

Dear FLUKA experts,

I am running a simulation on the ^{10}B(n, \alpha) reaction, and I want to score the energy of the neutron which interacted with ^{10}B. The geometry is a cuboid of pure ^{10}B , with a 5cm water layer in front of it. The primary particles are 1MeV neutrons.

image
image846×899 5.48 KB

I used USDRAW of mgdraw.f to print the energy. The code is:

      IF ( (ICODE == 300) .AND. (NP == 2) ) THEN
         WRITE (IODRAW,*) JTRACK, ICODE, LTRACK, (ETRACK - AM(8)), PTRACK,
     &                    KPART(1:NP), TKI(1:NP)
      END IF

And the results is like:

image
image1863×737 182 KB

The printed data appears to be the ^{10}B(n, \alpha) reaction events. Which confused me is that the energy of the neutrons is not as randomly as I thought. The energy is just some particular discrete values instead of a random continuous distribution. Regardless of the generation number (LTRACK), the neutrons will always have the same energy (as shown in the highlight in the figure above).

I would like to know what causes such a result, is it because of the energy group setting of the low energy neutrons? And is there any other way to obtain the energy of the neutrons participating in the ^{10}B(n, \alpha) reaction?

2

Dear @Jungle,
Could you please share your .flair file and all the user routine you are using?

3

@amario
Sorry to reply to you so late!
There was a mistake above. The neutron energy was set as 2.5e-11[GeV]. And the files are attached below:

bn.flair (2.7 KB)
bn.inp (2.7 KB)
m2.f (11.8 KB)

4

Dear @Jungle,

The repeating values of neutron energy are due to the multigroup transport approach used by Fluka. Neutrons having the same values belong to the same group.

As per your second question, unfortunately there is no other way to obtain the neutron energy.