AmBe source simulation

Dear Experts,

I wish to learn neutron transport using Fluka.

  1. The source is Am-Be source. I started with an alpha particle at (0,0,0) and target is Be-9.
    How should I score neutron dose rate in air at 1m ? I tried scoring but the results are not matching with literature data. Say, o/p from USRBDX when multiplied with neutron yield and flux to dose rate conversion factor (for average neutron energy 4.4 MeV), i should obtain the neutron dose rate - am I doing it correct ? As I intend to further solve neutron shielding problem, I chose to use a single energy (average for Am-Be source, from literature). (i/p: alpha1ambe.flair)
  2. I tried starting with 4.4 MeV neutron in BEAM, I could score neutron dose rate in air. But with HDPE as shield material, I could not get the expected neutron dose rate. (i/p: 2511ambe2b.flair)

Secondly, how to get the gamma dose rate as the decay of C-12* will give 4.43 MeV gamma, how to obtain this gamma and associated gamma dose rate at 1m ?
I refered some Fluka inputs which attempted the same, but could not follow them completely.
Please suggest/help.
PFA my input files.
Raksha Rajput
alpha1ambe.flair (1.8 KB)
alpha1ambe_22_sum.lis (4.2 KB)
alpha1ambe_21_sum.lis (81.4 KB)
2511ambe2b.flair (6.3 KB)
2511ambe2b_21.bnn.lis (4.6 KB)

Dear @raksha,

Please take a look to the following posts, which may be of help:

As mentioned in one of them, for simulations involving an Am-Be source, the recommended approach is to start the simulation directly from the neutron spectrum. To learn how to sample from a given spectrum take a look to

Then, seems that you are interested in dose equivalent (correct me if I am wrong), you can simply set an USRBIN scoring DOSE-EQ, whose results will be in pSv/primary. To transform to equivalent dose rate you just need to properly normalize using the activity of your sample.

Not sure what you mean by “I could not get the expected neutron dose rate”, could you elaborate?

Regarding the gamma, it is generated when you start from the alpha particle in the Be target but, since I just recommended to start from the neutron spectrum, you could run a second simulation, this time with a 4.43 MeV photon beam (instead of a neutron one). The dose can be obtained as in the previous case (USRBIN).

Hope this helps.

Kind regards,

A post was split to a new topic: AmBe source normalization issue