Re: [fluka-discuss]: Stopping powers for proton therapy applications

From: Anna Ferrari <>
Date: Mon, 11 Aug 2014 14:55:41 +0200

Dear Ana, dear Luke,

Stopping powers as printed in FLUKA output refer to momentum loss (dp/dx), not
to energy loss (dE/dx) as reported by NIST. If you did not take into account
this difference you compared different quantities and this can explain the
"discrepancies" you see.
At high energies the value of proton momentum is very close to energy, so
FLUKA numbers seem to agree with NIST. But at lower energies, and especially
for particles heavier than protons, there can be no agreement. In the case of
Ana the discrepancy -as expected- can be observed better for graphite, which
has half density compared with water.

This point was already clarified by Mario Santana:

Hope this helps,
best regards,

Anna Ferrari
Institute of Radiation Physics
Helmholtz-Zentrum Dresden-Rossendorf e.V.

Am Fri, 11 Jul 2014 14:05:21 +0000 schrieb "Ferreira De Almeida Lourenco, Ana"
> Dear FLUKA experts,
> I'm using FLUKA for clinical proton dosimetry applications. For validation
>proposes, I'm comparing the stopping powers from FLUKA with the stopping
>powers from ICRU.
> The graph below shows the ratio between FLUKA and ICRU stopping powers for
>water (blue) and graphite (green). As you can see I get a good agreement for
>water, but for graphite, specially for low energies. Could please someone
>explain me why do I get this disagreement for graphite? I'm using the same
>I-value (78eV) and density ( that ICRU uses for graphite.
> [cid:8c77f38a-d52f-4644-8e83-71ffc41c5a3a]
> Please find attached my inp file.
> Many thanks,
> Ana
Received on Mon Aug 11 2014 - 16:32:34 CEST

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