Hello Hayley,
I think your foil may be too thin and your hadronic inelastic interactions - overbiased.
You can redefine your target material(s) (using MATERIAL card) with lower density and increase the target thickness so that you end up with the same g/cm^2. Using 1E-2 in WHAT(2) of LAM-BIAS is a reasonable value from my experience. I would also use WHAT(4) to define which particles the biasing applies to (even though the default may be protons).
RADDECAY - if you would like to kill both electromagnetic cascade and transport of decay radiation, set WHAT(5) of RADDECAY card to 9999999999.
There is no normalization needed to correct for the use of LAM-BIAS, FLUKA takes care of it all. However, the RESNUCLE units will be Bq/cc only if you assign the correct volume of the scoring region in WHAT(6). Otherwise it is Bq per region. I'm not sure why you are scoring RESNUCLE in all regions. Don't you wont to score it in the region called FOIL?
I have attached a modified version of your input file that you may find useful.
Cheers
- George
----- Original Message -----
From: "hayley smith" <hayley.smith_at_stfc.ac.uk>
To: "FLUKA Discussion List" <fluka-discuss_at_fluka.org>
Sent: Monday, February 16, 2015 11:44:29 AM
Subject: [fluka-discuss]: RESNUCL with LAM-BIAS
Hi
I am trying to look at the residual nuclei produced when a 70 MeV proton beam repeatedly passes through a thin (on the order of microns) foil. I am trying to understand the different residuals, and proportions of residuals, produced by different foil materials (carbon, aluminium etc) and I have a few questions about my methods:
From reading many of the previous FLUKA discuss posts I have understood that on these short length scales it is necessary to use LAM-BIAS to reduce the nuclear interaction length. At 70 MeV the .out file showed that the inelastic interaction length was 34.31 cm in carbon so I reduced the interaction length by 1e-6 using the LAM-BIAS card. Is this a reasonable scaling factor?
I am now looking at the RESNUCL output that I get but am confused about interpreting the results, even after consulting previous discussion list posts and the notes from the most recent course. I have tried repeating the simulation with LAM-BIAS for different numbers of primary particles (1000 - 50000) and different scaling factors to get an understanding. In my simulation I assume a proton distribution of 1.25e15 protons per second. I have looked at the .out files and .lis files but I am still unsure - do I need to apply any weighting to the RESNUCL output or has this already been taken into account when the Bq/cc are processed?
And are there any other settings that I may be missing in my very simple input file (attached) that would allow me to get a useful simulation of the residuals?
Many thanks for any clarification you are able to give,
Hayley
Hayley Smith
ISIS Facility
Rutherford Appleton Laboratory
Harwell Oxford
OX11 0QX
01235 445524
hayley.smith_at_stfc.ac.uk<mailto:hayley.smith_at_stfc.ac.uk>
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Received on Thu Feb 19 2015 - 16:49:25 CET