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PostPosted: Fri Nov 05, 2010 4:53 am 
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Joined: Mon Jan 19, 2009 9:48 am
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Location: INFN Perugia
Hello,
two distinct questions:

1) injection spectrum

the Galdef option "inj_spectrum_type = beta_rig"
is considered in line #64 of "create_transport_array.cc".
Here's the code:

//if(strcmp(galdef.inj_spectrum_type,"beta_rig")==0) spec_shape*=particle.beta[ip]; // IMOS20000615
if(strcmp(galdef.inj_spectrum_type,"beta_rig")==0) spec_shape/=sqrt(1.+pow(2.e3/particle.rigidity[ip],2)); // IMOS20011210

If I don't make a misunderstanding, the first line (commented) corresponds to a real rigidity power law x beta (i.e. what the user expects from the choice "beta_rig").
Second line (adopted) gives the same rigidity shape for all charged CRs (at injection). But it is "beta_rig" only assuming M/Z = 2GeV for all particles (included protons, on which M/Z~1 GeV). It seems to me a crude approximation.
So I wonder what was wrong with the first line... ?


2) network iterations

In public GALPROPs, the option "network_iterations" is 1 by default.
Since some "special" channels seem not to respect the top-bottom fragmentation sequence (like 10Be->10B decay; hope it is clear what I mean),
I wonder if these "special" channels require some more iterations (2?) to be considered (and give the correct abundances).

I don't see this option in the WebRun online-interface. What's its default setting?
Why don't make it specifiable by the user?


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PostPosted: Fri Nov 05, 2010 6:14 am 
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Joined: Wed May 17, 2006 7:02 am
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Location: MPE Garching
2) to see it click on 'advanced user' and 'fixed parameters'.
You will see it is fixed to 2 which indeed covers the case you mention (probably the only one but important for B/C).
It is indeed there for the reason you mention. 2 is always enough as far as I know (though never checked in detail - would be worth trying 3 so see).
I agree it should be free (with default=2) since for some things (e.g. gamma rays) it is redundant, and sometimes it is useful to check the effect by changing it.

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Andy Strong, MPE


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PostPosted: Fri Nov 05, 2010 6:34 am 
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Location: MPE Garching
1) thanks for finding this. I don't know what is going on here offhand, unfortunately the change was not documented in the code.
It also needs to be put into the Explanatory Supplement Section 5.5.1.
Normally we use only rigidity without beta, so this was probably not tested much.

NB these comments are OK here but even better under BUGS? than FORUM since more likely that developers see them.
I copied them here with my replies:
http://galprop.stanford.edu/bugs/show_bug.cgi?id=39
http://galprop.stanford.edu/bugs/show_bug.cgi?id=38

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Andy Strong, MPE


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PostPosted: Fri Nov 05, 2010 7:44 am 
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Joined: Mon Jan 19, 2009 9:48 am
Posts: 19
Location: INFN Perugia
Andy, thank you for your prompt answer.

1) I did not think to it as a bug. Such spectral shape, only rigidity-dependent, is physically plausible as well as the broken one, often used. However the user should be aware of this, and it can be interested in a real "beta x rig" injection.
I also suggest to consider powers of beta (beta^W x rig), with W free parameter to be used instead of nuc_g_1 (that can be fixed =nuc_g_2).

2)Yes, when the user does not need >1 iterations, this option would save much cpu time on your farm.

NT

strong wrote:
1) thanks for finding this. I don't know what is going on here offhand, unfortunately the change was not documented in the code.
It also needs to be put into the Explanatory Supplement Section 5.5.1.
Normally we use only rigidity without beta, so this was probably not tested much.

NB these comments are OK here but even better under BUGS? than FORUM since more likely that developers see them.
I copied them here with my replies:
http://galprop.stanford.edu/bugs/show_bug.cgi?id=39
http://galprop.stanford.edu/bugs/show_bug.cgi?id=38


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PostPosted: Fri Nov 05, 2010 7:47 am 
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Joined: Wed May 17, 2006 7:02 am
Posts: 285
Location: MPE Garching
1) we need a more general form, and to document where the current form actually comes from.
2) the farmers would be happy indeed.

for further exchanges best to continue here:
http://galprop.stanford.edu/bugs/show_bug.cgi?id=39
http://galprop.stanford.edu/bugs/show_bug.cgi?id=38

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Andy Strong, MPE


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PostPosted: Fri Nov 05, 2010 9:40 am 
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Joined: Mon Jan 19, 2009 9:48 am
Posts: 19
Location: INFN Perugia
(posted in Bugzilla / reported here for completeness)

Hello. Just for the record,
I have quickly inspected the effect of using N=3 iterations instead N=2.
In the 10Be and 10B fluxes (the most sensitive ones to N), the difference is within ~0.1% or less at few GeV/n, and vanishes at higher energies, as I expected.
(Tried with v50p under some arbitrary configuration).


strong wrote:
2) to see it click on 'advanced user' and 'fixed parameters'.
You will see it is fixed to 2 which indeed covers the case you mention (probably the only one but important for B/C).
It is indeed there for the reason you mention. 2 is always enough as far as I know (though never checked in detail - would be worth trying 3 so see).
I agree it should be free (with default=2) since for some things (e.g. gamma rays) it is redundant, and sometimes it is useful to check the effect by changing it.


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