Dear Anton,
Many thanks for your e-mail and your thoughts.
You are right, I can simulate a few positions and extract from each a correction factor.
Many thanks,
Ana
________________________________
De: Anton Lechner <Anton.Lechner_at_cern.ch>
Enviado: 22 de julho de 2015 13:04
Para: Ferreira De Almeida Lourenco, Ana; fluka-discuss_at_fluka.org
Assunto: RE: Simulate unusual experimental setup: source to detector distance fixed
Dear Ana,
I would say the first question to ask is not how to specifically implement your setup in FLUKA, but rather if the experimental conditions allow to reasonably approximate all measurement points with a single simulation setup (like the one I described in my first Email) or if experimental conditions changed such that different setups have to be used.
Assuming that the divergence of the beam is indeed so large that the proton spot size on the front face of the phantom changes significantly when you displace your phantom by some tens of cm, then the experimental conditions have changed between measurement points (contrary to the case where you keep the phantom position fixed and you always have the same spot size on the phantom front face). Of course, now the key question is if this difference in spot size affects your measurements. This evidently depends on different factors like the actual beam size and divergence, the sensitive volume of your detector, etc. It might well be that you are not sensitive to this and then one simulation setup is sufficient. If you are sensitive, then you could consider to simulate a few positions (evidently one doesn't need 2500 different setups as small shifts of the phantom will certainly not affect the results).
Apart from that, it is of course beneficial to incorporate accurate phase space information about the incident protons in the FLUKA setup, but I don't really see how this would safe you CPU time.
Cheers, Anton
________________________________
From: Ferreira De Almeida Lourenco, Ana [am.lourenco_at_ucl.ac.uk]
Sent: 22 July 2015 11:20
To: Anton Lechner; fluka-discuss_at_fluka.org
Subject: Re: Simulate unusual experimental setup: source to detector distance fixed
Dear Anton,
Thank you for your e-mail.
In this case the beam divergence is not small because it consists on a scattering system. Is it possible to save the phase space information that comes out from the nozzle and use that as a starting point for the following simulations? This could potential reduce the CPU time.
Many thanks,
Ana
________________________________
De: Anton Lechner <Anton.Lechner_at_cern.ch>
Enviado: 21 de julho de 2015 12:22
Para: Ferreira De Almeida Lourenco, Ana; fluka-discuss_at_fluka.org
Assunto: RE: Simulate unusual experimental setup: source to detector distance fixed
Dear Ana,
Assuming that the beam divergence is small, then you could simulate your setup in the same way as the first setup you described, i.e. you keep the water phantom fixed in the FLUKA geometry and you introduce a USRBIN segmented in beam direction, which represents the different detector positions wrt phantom. In other words, the FLUKA coordinate system is moving with your phantom and the source position in the FLUKA geometry represents different positions along the beam.
Cheers, Anton
________________________________
From: owner-fluka-discuss_at_mi.infn.it [owner-fluka-discuss_at_mi.infn.it] on behalf of Ferreira De Almeida Lourenco, Ana [am.lourenco_at_ucl.ac.uk]
Sent: 21 July 2015 13:34
To: fluka-discuss_at_fluka.org
Subject: [fluka-discuss]: Simulate unusual experimental setup: source to detector distance fixed
Dear Fluka experts,
Usually, in order to get a depth-dose curve of a radiotherapy beam, the source to (water) phantom distance is fixed and you would move your detector downstream of the source in order to increase the amount of water upstream of your detector. This is very easy to simulate in FLUKA using a USRBIN card.
In my specific experiment setup, the source to detector distance was kept fixed, and the water phantom was moved towards the beam in order to change the amount of water upstream of the detector. I would like to simulate this experiment using FLUKA and I would like to know if there is a way of doing it, without having to run multiple simulations with different phantom positions (for example, for a 200MeV proton beam, the range in water is about 25cm, so to get a resolution of 0.01mm I would need at least 2500 simulations).
Many thanks,
Ana
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Received on Fri Jul 24 2015 - 13:09:08 CEST