RE: Disparity in Results between FLUKA & MCNPX

Daniela,

In my case I found good agreement behind the beam dump, it's only in
front of the beam dump (opposed to the beam direction) where I appear to
see the problem! Thank you for your suggestion regarding the stopping
power interpolation within MCNPX, I wasn't aware of this. However I
agree, I don't think this is the root cause as my colleague is having
similar issues with a more compact (but similar material-wise) 200 MeV
electron beam dump.

It seems that any light anyone can shed on these differences could help
both of us!

Best regards,
Lewis.

-----Original Message-----
From: Daniela Kiselev [mailto:Daniela.Kiselev_at_psi.ch]=20
Sent: 06 July 2011 16:41
To: Macfarlane, Lewis
Cc: fluka-discuss_at_fluka.org
Subject: Re: Disparity in Results between FLUKA & MCNPX

Dear Lewis,
it seems to me that we are doing almost the same! We are working on a
beam dump design for SwissFel, 7 GeV Electrons, at PSI. The materials
are almost the same: carbon, iron, (heavy) concrete. However, the
dimensions are quite different (more iron, less concrete). Recently I
made a comparison FLUKA-MCNPX2.7a. I compared the neutron dose behind
the beam dump. In this case I found that FLUKA leads to a factor of 2-3
higher dose rates.

MCNPX can take electrons up to 1 GeV only. The stopping powers are then
extrapolated to higher energies. Maybe, this extrapolations work not for
all materials. On the other hand, photonuclear cross sections are=20
available up to 100 GeV. This is the reaction which finally produces the
neutrons. Therefore, I have my doubt if this is the reason for the
discrepancy.

For which project are you working?

Best regards,

Daniela
Received on Thu Jul 07 2011 - 17:27:28 CEST