No deuteron scored for low energy helium-beam interaction on deuterium

Dear FLUKA expert,

I have a question, I am calculating cross-section for the elastic recoil of deuteron for low energy helium ions(<10MeV), and compare the results with experimental results in literature. The Alpha-Particle energy is 10MeV, the target is heavy water of 0.01cm, but there is no deuteron scored, is it a problem of the FLUKA model? Here are my input file and the reference.
10MeV-He+d.inp (9.2 KB)

Dear FLUKA user,

If I understand correctly, you’re shooting an alpha beam on a target containing deuterium and would like to score elastic deuteron recoils, i.e. deuterons produced not as a result of a nuclear inelastic interaction (involving mass transfer or at the very least some excitation energy), but instead knocked out in the course of elastic scattering of the alpha particle on either the electrostatic or the nuclear potential of target deuterium.

This will not work easily/yet in FLUKA as it stands now on two accounts:

  • Concerning nuclear elastic scattering, it is not implemented for ions with A>1 like you have here (one would actually need here the nuclear elastic scattering of deuterium on alpha in inverse kinematics).

  • Concerning Coulomb scattering, even if you’d switch to single scattering, only the deflection of the alpha would be accounted for, not the explicit deuteron recoil production and possible transport thereof (it is accounted in an effective way via nuclear stopping power but this does not involve the explicit production or transport of the recoil).

With kind regards,


Dear Cesc,

Thank you for your patient reply. The problem is I don’t score any deuteron in the energy 10MeV, but when I change the energy to 100MeV, there are deuterons scored. It looks like there is no nuclear reaction at low energy, so I want to know the reason why there is no deuteron scored below 10MeV. Thank you!

Hello Lichen,

The d you are seeing are indeed not from elastic recoils as per your expectation in your original question, but rather secondary deuterons from the following nuclear reactions (i.e. from nuclear inelastic processes), where I indicate the alpha threshold kinetic energy between parentheses:

a + d ---> p + d + 3H   (Ekin_thr=59.3 MeV),
a + d ---> n + d + 3He  (Ekin_thr=61.6 MeV),

maybe even

a + d ---> 3d           (Ekin_thr=71.4 MeV).

For a+1H, thresholds seem to be somewhat higher for producing d (unless i screwed up the arithmetics in this quick check). If you’re running on heavy water with O in natural composition (16O predominantly, with a bit of 17O and 18O), you may also see deuteron ejectiles from e.g.:

a + 16O ---> d + 18F    (Ekin_thr = 20.4 MeV)
a + 17O ---> d + 19F    (Ekin_thr = 12.4 MeV)
a + 18O ---> d + 20F    (Ekin_thr = 14.0 MeV)

This list is of course not exclusive: there can be other channels where additional ejectiles (e.g. n, p, etc) are emitted along with the d.

Note that the comment on elastic recoils in the reply to your original question still stands.


Hello Cesc,

Thank you again for your detailed reply! Then I understand, in FLUKA can only score deuterons produced by nuclear inelastic interaction, it’s currently hardly to score elastic deuteron recoils, is that right?


As suggested in the first reply, one cannot score recoils from nuclear elastic scattering events of projectile ions with A>1 impinging on a target deuterium. No explicit recoil production from elastic scattering on the Coulomb potential either (effective account via nuclear stopping power instead).

For completeness: you would see explicit deuteron recoils (above transport threshold) from nuclear elastic scattering on deuterium if the impinging particle were a proton above 10 MeV, or a neutron.