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elastic neutron scattering in Geant3 [message #10008] Thu, 21 January 2010 18:17 Go to next message
David Barton is currently offline  David Barton
Messages: 2
Registered: January 2010
occasional visitor
From: *scitech.temple.edu
I'm trying to output the energy loss and interaction position for ~1 MeV neutrons elastically scattering in my detector. I'm using the GCALOR package to process the events and I'm getting somewhat strange results. I'm finding large reductions in the kinetic energy of the neutron (up to >90%) which seems impossible for elastic scattering in my material. It seems that I must be getting inelastic events mixed in, but the rate seems rather high and these event don't appear at all when I'm looking for events that have a total energy loss (DESTEP > 0). I'm monitoring IPART for my events and all of the events have a neutron coming out, but when I look at only events where DESTEP is > 0 I only get protons out. [Is there a parameter that looks at the total energy of your initial particle? DESTEP seems to be the total energy of the total interaction]

I'm really not sure if I'm doing something wrong, if there is a problem with the program or if the results are correct, but I figure it probably is something that I'm doing wrong. If anyone has any advice related to neutron elastic scattering that would be great.
Re: elastic neutron scattering in Geant3 [message #10009 is a reply to message #10008] Thu, 21 January 2010 19:50 Go to previous messageGo to next message
Mohammad Al-Turany is currently offline  Mohammad Al-Turany
Messages: 518
Registered: April 2004
Location: GSI, Germany
first-grade participant
From: *dip.t-dialin.net
Hi,

First of all are you using the vmc (i.e PandaRoot) or the native fortran stuff?

I am not sure I understand what you are doing but the DESTEP is the total energy lost in one (current) step, and not for the total energy loss in material.

Quote:

I'm finding large reductions in the kinetic energy of the neutron (up to >90%)


How did you measure this, did you look at GETOT?


Also what cuts are you using, I assume you change the default if you are using 1 MeV neutrons.

regards

Mohammad
Re: elastic neutron scattering in Geant3 [message #10012 is a reply to message #10009] Thu, 21 January 2010 21:20 Go to previous messageGo to next message
David Barton is currently offline  David Barton
Messages: 2
Registered: January 2010
occasional visitor
From: *scitech.temple.edu
I'm using the native fortran stuff. For the kinetic energy I'm using GEKIN, and I'm using a 1 keV cut for the neutrons.

I see now that there is a GETOT parameter, but I guess what I really would like is something that looks at the energy lost by the particle in each step, similar to DESTEP. But this isn't my biggest problem. The real problem is the very large energy losses.

Thanks

David
Re: elastic neutron scattering in Geant3 [message #10013 is a reply to message #10012] Thu, 21 January 2010 22:20 Go to previous message
Mohammad Al-Turany is currently offline  Mohammad Al-Turany
Messages: 518
Registered: April 2004
Location: GSI, Germany
first-grade participant
From: *dip.t-dialin.net
Hi,

How can you get very large energy losses and at the same time you wrote:

but when I look at only events where DESTEP is > 0 I only get protons out


So maybe something is wrong in the way you register your hits!

When using GCALOR the energy cut-off for neutrons CUTNEU has to be set to a reasonable value (you can go down to 10E-14 GeV), GEANT will complain but you can ignore the warning. Also the time cut-off has to be set to a value, which allows to track the very slow energetic neutrons till they are captured or fall below the energy cut-off.

What kind of detector you are simulating? and Why with native FORTRAN?

Mohammad
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