Re: [fluka-discuss]: Energy deposition not all from electronic stopping power?

From: Francesco Cerutti <>
Date: Wed, 27 Jun 2018 11:07:22 +0200

Hi Ryan,

you are missing the fundamental concept that stopping power is not
constant. It's increasing for decreasing energy (your proton is losing
energy through the slab), which explains the higher energy deposition you

Moreover, note that your expectation misses also the fact that delta
electrons, generated by proton induced ionization and contributing to the
proton stopping power, may actually leave your reference volume and
deposit some energy outside.

Kind regards


Francesco Cerutti
CH-1211 Geneva 23
tel. +41 22 7678962
fax +41 22 7668854

On Wed, 27 Jun 2018, Ryan Brosch wrote:

> Dear FLUKA experts,
> I have a simple setup of a 200 MeV proton beam incident on a 1mm slab of
> water. I am scoring energy deposition with SCORE.
> The stopping power for a 200 MeV proton is 4.491 MeV/cm or 449 KeV in a 1mm
> slab. 
> However, SCORE shows about 463 KeV of energy deposition, 14 KeV more than
> expected. This is to much energy to be from nuclear stopping power.
> Am I missing some physics here? Surely the energy deposition should be
> almost entirely due to inelastic coulomb scattering and should just be
> dE=(dE/dz)dz where dE/dz is the stopping power.
> Thanks very much,
> --
> Ryan Brosch
> Ph.D Candidate
> Department of Physics
> Arizona State University

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Received on Wed Jun 27 2018 - 21:32:58 CEST

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