|Message: Secondaries from heavy-ion projectiles with different physics lists||Not Logged In (login)|
Click on the Forum title, e.g. on the "Forums by Category" page, to read a sequence of postings to the Forum and its threads all in one page. If you are only interested in one thread or the thread following a specific posting, click the thread or the posting, which takes you to a smaller page, which contains only the part you are interested in and may be easier to navigate.
Messages are "chained" if there are only replies at the first level, i.e. 1/1.html, 1/1/1.html etc. In case of "chained" messages the message number is replaced by the icon and there is no indentation.
Inline: Display the subject line only or also the text of the posting(s); for the choice "All" the "Outline" choices are switched off.
|1||0||1||no text / full text of posting|
|2||1||All||text for level 1 only / text for All postings|
Outline: Choose the depth of the posting thread, successive toggle controls provide increasing detail.
|1||2||1||2 levels / 1 level (original posting)|
|2||3||2||3 levels / 2 levels|
|3||3||All||3 levels / all levels (all postings)|
I'm trying to choose a physics list to bombard space materials with heavy-ion galactic cosmic rays (about 10 MeV/nuc to 10 GeV/nuc). To help me decide, I ran some simple simulations of monoenergetic beams normally incident on one side of a one-centimeter aluminum slab, tabulating all particles that escaped from either side of the slab.
The attached files show the results for protons coming off the back (incident) side of the slab for 12C projectiles, using the QBBC_EMZ and Shielding_LIV reference physics lists. The logarithmic colorscale shows the intensity of secondary protons at a given energy (vertical axis) produced by carbon projectiles at a given energy (horizontal axis), integrated over all angles (going backward relative to the original carbon beam).
If you download the images and toggle between them, you'll see a "background" population of protons below a couple of hundred MeV in both plots, but with another population produced by higher-energy carbon nuclei added to it. For the Shielding physics list, the second population starts appearing when carbon energies exceed about 100 MeV/nuc, and the proton energies aren't that much higher than those of the first population; for the QBBC physics list, the second population turns on much more sharply above about 2 GeV/nuc carbon, and proton energies extend up to 1 GeV or so. Similar patterns are apparent for other many other primary and secondary species that I looked at.
Does anybody have insight into what is causing this difference, and which is a better representation of the real world (or is another list better than either)? This is exactly the range of energies, of both primaries and secondaries, that I'm interested in, so I'd very much like to get it right! Many thanks.
Attachment: http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/06/13/18.21-35186-qbbc_emz.png http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/06/13/18.21-90924-shielding_liv.png
|Inline Depth:||Outline Depth:||Add message:|