Dear Yung-Shun,
it is a bit difficult for me to compare the two graphs which you have attached because they show different quantities and units. But I don’t think that you’re doing something wrong.
The reason is probably the rather intricate reaction 7Li(p,n) which is difficult to model in the framework of an INC. For light isotopes like 7Li the results of pre-equilibrium and equilibrium decay theories using an optical potential are somewhat approximate as the nuclear levels are widely spaced and the statistical assumptions of the models can be too coarse for detailed simulations. This problem has been discussed in detail in related papers.
Usually you will get two rather broad bumps at the top of the spectrum and a peak which is too low, instead of the sharp and high peak that is known from measurements. We have seen this with several MC codes (FLUKA, MCNPX and previously also PHITS). As you can see the introduction of a specific perturbation-theory based approach in PHITS for this purpose is rather recent and required quite some fine-tuning.
This specific Li7 reaction has been used by us in collaboration with some of the authors of the quoted paper for a number of instrumentation tests. Therefore, the Japanese colleagues made quite some effort to eventually be able to accurately reproduce the reaction which we used during the experiments. But I would not expect to see this soon as an “out-of-the-box” feature in other general purpose MC codes as well. In the end it is a rather specific case and requires a specialized solution.
Best regards
Chris
From: owner-fluka-discuss_at_mi.infn.it [mailto:owner-fluka-discuss_at_mi.infn.it] On Behalf Of Yung-Shun Yeh
Sent: 23 March 2016 16:34
To: fluka-discuss <fluka-discuss_at_fluka.org>
Subject: [fluka-discuss]: the neutron spectrum of 7Li(p, n) reaction
Dear FLUKA experts,
Recently I am simulating the neutron spectrum of 7Li(p, n) reaction by using a 230MeV proton beam bombarding lithium-7 target. I am trying to reproduce the neutron spectrum in attached figure from the reference
http://www.sciencedirect.com/science/article/pii/S1876610214026988. The neutron energy is a qusi-monoenergetic energy peak in the paper.
But my result is quite different from the paper. The energy is a broad distribution.
I am just wondering if I did something wrong. How do I get similar result to the reference?
The simulation setup is as the following: proton beam with 230 MeV kinetic energy collide the 10mm thick lithium-7 target. the neutron fluence is recorded at the other side of lithium target. The solid angle for scoring is set to be 0.00628 which is closed to 0 degree.
The input card is also attached.
Thanks for your great help,
Yung-Shun
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Received on Thu Mar 31 2016 - 13:50:39 CEST