[fluka-discuss]: Logarithmic width of dp/dx momentum loss

From: Anton Lechner <Anton.Lechner_at_cern.ch>
Date: Sun, 3 Mar 2019 21:11:48 +0000

Dear Delmon,

I think you misunderstand the meaning of this parameter, i.e. the "logarithmic width of dp/dx momentum loss for hadron/muon" does not control the fractional energy loss of these particles, but it represents the granularity of the stopping power tables created by FLUKA in the initialization phase. More precisely, it is the ratio E_i+1/E_i, where E_i is the i_th energy at which the stopping power is tabulated. The more bins you have (i.e. the closer this parameter is to 1.0), the more precise the representation of the stopping powers, however at the cost of CPU time. If you want to change this parameter, you can do this on the DELTARAY card (see WHAT(3) - alternatively you can also set the number of bins on WHAT(2) - see note 2 below the DELTARAY card in the manual). You may also print the stopping power tables, using SDUM=PRINT. Then you can see how this parameter changes the stopping power bins.

On the other hand, the fractional energy loss is indeed controlled via the FLUKAFIX card. Both PRECISIO and HADROTHErapy as DEFAULT gives you 0.05 (see note 2 under the FLUKAFIX card - at energies of a few tens of MeV a smaller value is effectively used).

Cheers, Anton

PS: your email didn't make it into my inbox (maybe it was filtered); hence I copied your email from the FLUKA webpage (http://www.fluka.org/web_archive/earchive/new-fluka-discuss/13765.html)

From: Delmon Arous <Delmon.Arous_at_rr-research.no>
Date: Sat, 23 Feb 2019 14:29:12 +0000

Dear FLUKA experts,

Firstly, I am a fresh FLUKA user. I am simulating a 16 MeV pencil-like proton beam impinging a modeled target cuvette containing DMSO and using PRECISIOn defaults. However, I see that the logarithmic width of dp/dx momentum loss for hadron/muon is set at 1.04 - how do I change this values to e.g. 1.03 for the protons when utilizing PRECISIOn defaults? Do I have to adopt the FLUKAFIX card? If so, what is the maximum fractional energy loss when the logarithmic width of dp/dx momentum is set at e.g. 1.03? How are these widths translated into fractional kinetic energy loss per step? Could someone elaborate this parameter for me?

Many thanks in advance for any response!

Best regard,


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Received on Sun Mar 03 2019 - 23:43:24 CET

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