[fluka-discuss]: RE: USRYIELD spectrum for PROTON and BEAMPART in SOBP beam

From: Anton Lechner <Anton.Lechner_at_cern.ch>
Date: Thu, 13 Jul 2017 12:32:58 +0000

Dear Francesca,

Without your input file and routines one cannot really judge what is going on. I guess you have your own source routine to simulate the different proton energies of the SOBP? Please send a minimum working example (for both cases, single energy and SOBP) which allows to reproduce the problem.

Cheers, Anton


________________________________________
From: owner-fluka-discuss_at_mi.infn.it [owner-fluka-discuss_at_mi.infn.it] on behalf of Francesca Fiorini [francesca.fiorini_at_oncology.ox.ac.uk]
Sent: 12 July 2017 16:13
To: fluka-discuss_at_fluka.org
Subject: [fluka-discuss]: USRYIELD spectrum for PROTON and BEAMPART in SOBP beam

Dear experts,

I am plotting the spectra of protons in water in the middle of a SOBP in a phantom. I am using USRYIELD, and in two different cards I'm scoring the spectrum for PROTON and BEAMPART. According to what I could understand from some emails in the mailing list and manual, BEAMPART should include incident protons plus those that only undergo elastic interactions, while PROTON should include all protons (primaries + secondaries). First of all, is this second assumption correct?

If it is, when I plot the USRYIELD data, I have the spectrum of BEAMPART way above the spectrum of PROTON (almost 10 orders of magnitude larger), which would make sense only if, for some reason, the BEAMPART and PROTON spectra were normalised using different numbers, or... I made some mistake somewhere.

However if I repeat the same simulation without using a SOBP, but a simple pencil beam (one single energy instead of many), I have no problem in producing sensible results, with the data from PROTON slightly higher than BEAMPART as it should be. I've also noticed that in the case of the SOBP, also other particle spectrum scorings from USRYIELD have a weird normalisation, as they are about 3x10^3 times larger than the case with only one single energy beam. While I expected the SOBP case to show a higher number of secondary particles, a ratio of this magnitude is perhaps a bit too large.

Does all of this depend on the fact that in the SOBP case there are many initial beams and FLUKA is not picking the exact total number of particles to do the normalisation? However why would it pick two different numbers for BEAMPART and PROTON?

I have used BEAMPART and PROTON before in USRBIN scorings and never found anything that didn't convince me, so I am uncertain here on how to treat these results.

If you could enlighten me on this I would be extremely thankful.

Many thanks
Francesca


CRUK and MRC Oxford Institute for Radiation Oncology
Department of Oncology, University of Oxford
Old Road Campus Research Building
Roosevelt Drive
Oxford, OX3 7DQ
UK

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Received on Thu Jul 13 2017 - 15:35:42 CEST

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