The neutron distribution in FARM photonuclear reactions is not displayed

Dear FLUKA Experts,

Recently, while utilizing the FARM module of Flair, I encountered a peculiar issue.

I conducted an simulation where a 15 MeV electron beam bombarded a tungsten target, resulting in the production of gamma rays. These gamma rays subsequently underwent photonuclear reactions with the tungsten, releasing neutrons.

To analyze the distributions of both neutrons and photons, I employed the USRBIN card. Within the FARM module, I utilized body27 to excise a portion of the geometric model, aiming to observe the distributions of neutrons and photons.

However, I was able to observe the photon distribution within FARM but failed to detect the neutron distribution. Conversely, when plotting the two-dimensional USRBIN graph in the plot module, the neutron distribution was visible.

I am uncertain about the underlying cause of this phenomenon and hope that the experts can provide some insights to resolve my confusion.

Thank you very much.


Fig 1 Photon distribution in FARM


Fig 2 Neutron distribution in FARM


Fig 2 Neutron distribution in plot

Flair flie:
White source.flair (11.5 KB)

Dear Yaoxuan,

I had a look at your file and I tried to run your simulation. I attach below the pictures of my results.

Photons:


Neutrons:

Both overlapped:

You say that you are using body27 for clipping, but such object does not exist in the file that you provided. Also, it looks like the the photon scoring on your picture is different than what I found in your file, as well as the missing target cylinder which in my case absorbs most of the photons.
My advice is (in order):

  1. Check if you are using the newest version of Flair and FLUKA.
  2. Check your geometry again and make sure that what you are scoring is what you want to see.
  3. Run more primaries - the results that I am showing were obtain with a total of 2e7 primaries.

Let me know if it works.

Cheers,
Jerzy

Thank you very much for your reply! I reinstalled my virtual machine and Flair resumed normal operation.