secondary neutrons missing from usrrnc.f

From: Shirley Li <>
Date: Fri, 31 Aug 2012 16:17:54 -0400

Dear fluka users,

I'm trying to simulate neutron yield from a muon beam passing through
water. I modified mgdraw.f and count neutron yield from every
interaction. The number is consistent with published results to about
10%. Then, I tried to compare neutron yield to residual nuclei, i.e.,
every time some neutrons get generated, there should be residual
nucleus produced at the same time. So I modified usrrnc to look at the
reactions/neutron yield. However, some low energy neutron interactions
look different in the outputs from mgdraw and usrrnc. In both
subroutines, I look at interaction by


do ip = 1, NP
   WRITE ( unit, *) ip, KPART(ip), TKI(ip)

do ipheav = 1, NPHEAV
   WRITE ( unit, *) ipheav, -KHEAVY(ipheav), TKHEAV(ipheav)

There are a lot of reactions reading from mgdraw.f output is a parent
low energy neutron generates one neutron. However, this reaction
seeing from usrrnc output is one parent neutron generates a 16O (since
it's in water) with NO child neutron. This also happens to some
similar reactions where basically it's low energy neutron bouncing off
nuclei and losing energy with no other real secondaries. However, the
neutron doesn't appear in usrrnc.f secondary but it does appear in
mgdraw.f secondary. Does anyone know why this is?


Shirley Li
Received on Sat Sep 01 2012 - 13:19:16 CEST

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