Write neutron rate profile from RABBIT to dd

[adrianaghiozzi]

See ProjectTorreyPines/RABBIT.jl#3 in RABBIT

[orso82]

@adrianaghiozzi I was wondering if RABBIT distinguishes between neutrons of different energies...

D+T→He4   (3.518 MeV)  + n (14.072 MeV) + 17.59MeV

D+D→He3   (0.8175 MeV) + n (2.4525 MeV) + 3.27MeV
D+D→T     (1.0075 MeV) + H (3.0225 MeV) + 4.03MeV

D+He3→He4 (3.66 MeV)   + H (14.64 MeV) + 18.3MeV

The more I look at core_sources.source[:].profiles_1d[].neutral as a way to store neutrons, the more I come to the conclusion that we should extend core_sources with core_sources.source[:].profiles_1d[].neutron. How about with something like this?

 neutrons[:]
 ├─ label [] {String}
 ├─ index [] {Int} # 1: fusion, 2:beam-target, 3:beam-beam
 ├─ energy [eV] {Float}
 ├─ particles [s^-1.m^-3] Vector{Float}
 └─ particles_inside [s^-1] Vector{Float}  # mostly for symmetry with electrons and ions particle sources, for us it will be an expression

[adrianaghiozzi]

I think this is a good idea in general but we wouldn't be able to apply it to RABBIT without directly editing the RABBIT source to give more outputs. Right now RABBIT sums up the neutron rate contributions of thermonuclear, beam-target and beam-beam reactions and writes only the summed result to file. Similarly it considers the neutron energies separately as well based on the reaction type at some point, but seemingly sums away the individual contributions.

See below comparing the output of RABBIT for the total neutron rate to the sum of the individual contributions which are output in this case by NUBEAM