Re: Finding out neutron capture location

From: Stefan Roesler <>
Date: Wed, 31 Jul 2013 23:03:30 +0200

Hi Matthew

No guarantee but this is what I would try:

- Modify mgdraw such that it creates only the output that you want in the
format you want..

- Print out under ENTRY ENDRAW all energy depositions with ICODE=30
(neutron kerma). Here you have access to the position (XSCO, YSCO, ZSCO)
and region number.

- Print out under ENTRY USDRAW secondaries from low energy neutron
interactions ICODE =300. The secondaries are in common GENSTK (kp=1,np).
Thus (to be tested), if called and NP=0 the neutron is absorbed. The
position is on (XSCO, YSCO, ZSCO), region number on MREG. The respective
energy deposition should be printed just above (from ENTRY ENDRAW) with
the same position.

You can call the modified mgdraw file as you like and you don't have to
overwrite the original in usermvax (don't do it). You have to compile this
new mgdraw file with fff or via Flair and link it into a new executable
with lfluka -m fluka -o myFluka my_mgdraw.o or via Flair.

The USERDUMP card looked ok. The output unit has to be whatever you use in

Hope it works,


On Fri, 26 Jul 2013, Balmer, Matthew wrote:

> I have modelled a simple scintillator loaded with boron with a neutron source. I want to know where (if it is captured in the region) in x,y,z co-ordinates the capture has taken place.
> I understand that the way to do this is to use USERDUMP? I have tried:
> USERDUMP 100.0 49.0 0.0
> Then I ran the mgdraw file through readfluka to try and get this into a readable format. But it doesn't seem to be what I want. What is the WHAT(2) code to get x,y,z for every step of the neutron?
> Can I get this information without needing to modify mgdraw? I don't mind getting more information than I need then writing a script to sort through the track information.
> If I do need to modify mgdraw, am I correct in my understand that:
> 1) I pick a number not in use for WHAT(2), say 80.
> 2) Then modify EEDRAW? to get the x,y,z location of where the neutron came to rest and was captured?
> 3) this modified mgdraw file can be named mgrdaw_mod.f and keep in the
> project directory? Or does it need to overwrite the mgdraw.f in the
> source directory?
> Apologies, I am a novice with this, I've been through the manual, the forum and some examples, and come to the above conclusion.
> Regards,
> Matt.
Received on Thu Aug 01 2013 - 09:35:11 CEST

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