# RE: [fluka-discuss]: Difference between FLUKA and NIST Unrestricted Electron Stopping Powers

From: Daniela Botnariuc <daniela.botnariuc_at_npl.co.uk>
Date: Wed, 27 Mar 2019 16:35:58 +0000

Dear Paola and FLUKA experts,

I tried to implement your suggestion by using the EMFCUT card but I believe I am still printing restricted stopping powers - and I need unrestricted stopping power values used by FLUKA. Please consider the figure below.

First, I set the photon production threshold to a very high energy value and this approximated my curve to the NIST curve for high energies. The electron production threshold was set to 100 keV (red curve).

Since I want to print unrestricted stopping powers, I then increased the electron production threshold to 10 MeV (yellow curve) and we can see that the values have better agreement to NIST. The problem is that with EMFFIX card I am only printing stopping powers for energies higher than the established threshold - and I also need stopping power values for low energies. How can I solve this problem?

Please find attached the input file I am using for this simulation.

Thank you very much.
Best Regards,
Daniela

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From: paola sala <paola.sala_at_cern.ch>
Sent: 22 March 2019 09:44
To: Daniela Botnariuc <daniela.botnariuc_at_npl.co.uk>; fluka-discuss_at_fluka.org
Subject: Re: [fluka-discuss]: Difference between FLUKA and NIST Unrestricted Electron Stopping Powers

Dear Daniela,
the DELTARAY cards controls delta ray production by hadrons and muons. It does not affect electron/positron transport.
The "delta ray production" threshold for electrons is the same as the electron production threshold, and is set through
the EMFCUT card with SDUM=PROD-CUT

Thus, you are printing RESTRICTED energy loss by electrons/positrons, with a threshold that depends on the DEFAULT and EMFCUT cards
you are using. This fully explains the supposed difference wrt NIST .

Please look in the manual for further information.

You can also have a look to the Ionization and Transport lectutr in the last fluka course
https://indico.cern.ch/event/694979/contributions/2927124/attachments/1657653/2654330/Ionization_and_Transport_2018.pdf

Have a nice day
Paola

On 3/21/19 4:36 PM, Daniela Botnariuc wrote:
Dear FLUKA experts,

I am simulating a proton beam in a water region where I am also considering secondary particles, including electrons. My goal is to print out the electron stopping power used by FLUKA and for that I activated the PRINT option in the EMFFIX card. To make sure I am getting unrestricted electron stopping powers, I set the DELTRARAY production threshold to infinite, so there is no delta ray production.

I compared the stopping power values printed in the output file to the NIST unrestricted stopping powers and I find a large discrepancy as you can see in the figures below.

Could someone explain why are these values so different? Am I simulating it wrong?
I have been trying to understand this for some time and I would really appreciate any help.

Best wishes,
Daniela

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Received on Wed Mar 27 2019 - 18:51:04 CET

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