Question: How to stop neutron transport below 1 MeV and beyond 20 MeV

From: Mohammad Islam <rafiqul.islam_at_okstate.edu>
Date: Mon, 2 Apr 2012 15:20:10 -0500

Dear Fluka Experts,

Many many thanks for helping me with my previous question on LOW-MAT.

I am modelling a simplified snout for proton therapy. Outside the snout, I
have placed a water phantom and inside the phantom I have placed several
CR-39 Plastic Nuclear track detectors. These detectors are tissue
equivalent and are placed at various angles and various distances from
isocenter. I want to calculate the dose equivalent at different locations
using these detectors due to the neutrons created in the snout and in the
phantom.

My question: CR-39 Detectors are sensitive to neutrons of about 1-20 MeV.
So I want to measure dose equivalent only from neutrons of 1to 20 MeV.
According to manual, the low energy neutron has a range of 1e-14 GeV to
0.02 GeV and after that fluka hadronic model takes over. But I want the
dose equivalent only from* 1-20MeV* of neutrons. If I use PART-THR card for
neutron cut-off I can stop neutron transporting with a energy lower than 1
MeV but how can I stop the neutron transport beyond 20 MeV.

To check that neutron transportation is stopped below 1MeV, I plotted
fluence graph for 226 MeV proton using USRCOL card which I attached here
with. But I dont know how to stop neutrons beyond 20 MeV at the same time.

Please help.

Thanks
Mohammad Rafiqul Islam
PhD student, Oklahoma State University
USA

Neutron_fluence_for_226_MeV_proton.jpg
Received on Tue Apr 03 2012 - 09:15:17 CEST

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