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None change in proton dose deposition from 4.9.1 to 4.9.2p2 

Forum: Hadronic Processes
Date: Nov 03, 14:09
From: Nicholas Remmes <Nicholas Remmes>

I have a very simple simulation of a monoenergetic and unidirectional, point source, 90 MeV proton beam into a 30cm deep box of water. The detector in the water is a 5cm diameter cylinder sectioned into 600, 0.5mm slices. I'm using the physics list directly from the hadr01 example code and selecting the QGSP_BERT_HP option.

When I run in v. 4.9.1, I get a smooth curve that matches published curves quite nicely.

When I run in v. 4.9.2p2, I get a curve that has several small peaks/undulations just proximal to the Bragg peak. In addition, the range is slightly greater in the newer version.

If I reduce the cut from the 1mm default to 0.01mm, the 4.9.2p2 anomalous structure disappears abruptly between a cut size of 0.05mm and 0.01mm (though some indication of the structure can still be seen at 0.01mm cuts).

I get the same result when I use the NIST G4_water as when I build the material by hand.

Any idea what's going on? Why do I have to use an order of magnitude smaller cut size in the later version to achieve similar results?

Thanks in advance for any insights you're willing to share.

Nicholas Remmes

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1 Idea: Re: change in proton dose deposition from 4.9.1 to 4.9.2p2   (Vladimir Ivanchenko - Nov 04, 02:06)
(_ Ok: Re: change in proton dose deposition from 4.9.1 to 4.9.2p2   (Nicholas Remmes - Nov 04, 10:50)
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