Production cross section via RESNUCLEI and USRYIELD

Dear experts,

Continuing the process explained here Ac225 and Ac227 cross sections for proton beam on Th232 target - #4 by ceruttif, in the present case (13 MeV p on Th232), I tried to get the formation cross section of few fission products. The USRYIELD result was smaller as compared to the published value (for e.g., for Kr 87, the simulation result 2.56 mb, where as literature value 7.9 ± 1.2, for Kr 88, the simulation result 7.04 mb, where as literature value 6.8 ± 1.3, for Sr 91 the simulation result 1.08 mb, where as literature value 8.5 ± 0.9 ).

Hence, I tried to get the values via using RESNUCLEI card, but it is showing 0 results for these products.

Can you please guide in this regard?

p_on_232Th_13MeV.inp (3.4 KB)

Literature Ref: Table 2, page 3014

PhysRevC.25.3011.pdf (695.4 KB)



This means that they all leave the target, and can be intercepted by USRYIELD.
Your estimates through the latter look consistent and point indeed to an underestimation, at least for two fragment types.
These fission channels correspond to only few percent of the total reaction cross section, but the reported underestimation may deserve some improvement attempt, we’ll try to pursue.

Thank you @ceruttif for the explanation.

In this regard,

  1. like you mentioned in the previous link, “since the Ac recoils mostly fall below the ion transport threshold, and therefore they are not intercepted by USRYIELD”, is there any parameter that is printed in FLUKA output which we can look for so that we can infer whether the recoil is below the ion transport threshold or not?

  2. As you mentioned above,

how to understand if a particular fission channel corresponds to only few percent of total reaction cross section?

Is it because the total sigma value written in first few lines of USRYIELD output is 629 mb, whereas sigma for Kr 87 is 7.9 (as per the literature) ? For Kr 88, sigma is 6.8; so does this mean contribution from these two reaction channels (Kr 87 and 88) is nearly same ?



  1. The concerned variable is the actual recoil kinetic energy, which is not a fixed parameter but naturally varies from a reaction to another. You can get it on an event-by-event basis through mgdraw_empty.f (USDRAW). Otherwise, the null result in either USRYIELD or RESNUCLE is already a patent indication of what is going on, namely the fact that the recoil remains at the generation location or manages to go away.

  2. Yes.

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Thank you @ceruttif for explaining. Just one more thing. If the recoil manages to go away from the generation location, can it be registered via RESNUCLEI card if a region is created surrounding the target (for e.g. the void region in this case) ? Or only USRYIELD is valid in such cases?



If it leaves the original region, it can indeed be scored by RESNUCLE in an adjacent region, provided that it actually stops there (which cannot be the case in vacuum).

Dear @ceruttif

I tried by setting void material AIR, but it gave error since in dE/dx, I have used AIR as material.

[*** Region 2 (VOID ) contains material AIR with is the alternate of material Th232 run stopped ***]

In this case, do I have to define a separate AIR material (may be with different name, but keeping other composition same) so that I can use it as void material as well as dE/dx in target material ??



In this case, in view of your target thickness and proton energy, I’d rather drop AIR as dE/dx material in the Th232 MATERIAL definition, since the proton energy loss across the target is anyway negligible.
Note that beam protons are in principle able to generate other reaction products directly in the now surrounding AIR.

Thank you @ceruttif for the detailed explanation.