[Clas_gsim] Help needed on GSIM FFREAD cards

[Harut Avakian]

Hello All,
Original version of the GSIM code had just one configuration with an 
additional target field, and that was the polarized target magnet.
That explains the notations with PTG. The geometry was hard-linked to 
magnetic field. Later on the softaware was generalized for any 
configuration with target field (solenoid, polarized target,HD-Ice,...). 
The field was also decoupled from the geometry, as other target magnets 
had a possibility to be shifted from the geometrical center of the 
target. Variables defining the type of the target magnet (TMGIFIELD) and 
the scale (TMGSCALE) use TM (means target magnet).
Other related card defines the center of the field (MGPOS).
All ffread cards with PTG  (excluding PTGMAXRAD which defines the 
maximum extension of the target field to be accounted in the simulation) 
are obsolete and should be discarded. If they appear in any ffky file, 
that is a bug.
Please follow FX's recommendations below.

Best regards,
harut

On 2/22/13 9:46 PM, Francois-Xavier Girod wrote:
>
> Dear Krishna,
>
> 1) only the 4 first letters are used, so this is the same card
>
> 2) in the current version of GSIM under
> /u/home/claseg4/software/packages/gsim
> I have found trace of PTGSCALE only in the readfile
>
> I have not found trace of PTMGSCALE
> I think the correct key is TMGSCALE
>
> Those statements are also true from the package version under the common CLAS environment.
>
> 3) still from the package under claseg4
> PTGFIELDM is in ffky_sol.F (Saclay solenoid)
> TMGFIELDM is in ffky_ptg.F (polarized target)
> Both of them set the same variable ptg_fieldm which is the _design_ maximum of the field
>
> my understanding is that both TMGSCALE and TMGFIELDM are used
> the default "maximum field" (design maximum) for ptg is 51 kG
> the default scale is 0.979
> so the actual maximum field by default is 49.92 kG
>
> If you specify TMGFIELDM = 49.92 and TMGSCALE = 0.979
> then the resulting maximum field would be 49.92*0.979 !
> (disclaimer : that is my understanding from a grep of the variables in the source code directory)
>
> 4) I did not find a key PTGIFIELD but I did a key find TMGIFIELD
> this key sets the internal variable ptg_ifield
> ptg_ifield = 1 -> polarized target
> ptg_ifield = 2 -> Saclay solenoid
>
> 5) see 4)
>
> I hope that helps. I suppose someone more familiar with eg4 simulation should look into this.
>
> Best regards,
> Francois
>
> ----- Original Message -----
> From: adhikari at jlab.org
> To: "clas gsim" <clas_gsim at jlab.org>
> Sent: Friday, February 22, 2013 8:08:39 PM
> Subject: [Clas_gsim] Help needed on GSIM FFREAD cards
>
> Can anyone explain to me the difference between the following cards?
>
> 1) BAFF & BAFFES - Which one is the correct card name for the Baffels -
> BAFF or BAFFES? I have seen BAFF used & the following reference page only
> lists BAFFES? Should either one work or are they different?
>
> 2) PTGSCALE & PTMGSCALE : Equivalent?
>
> 3) Is it redundant to use both PTGFIELDM, & PTGSCALE. If not what's the
> difference?
>
> 4) How about PTGIFIELD? And, what should be the value to simulate for the
> EG4 experiment which used polarized NH3 & ND3 targets (with 5T=50kG
> field)? There doesn't seem to be enough information in the only reference
> (http://nuclear.unh.edu/~maurik/Gsim/gsim_doc_ffread.shtml) that I could
> find.
>
> 5) Now, I have seen other people also using TMGIFIELDM. May I know what is
> the difference between TMGIFIELDM & PTGFIELDM?
>
> Any bit of information will be greatly appreciated.
>
> With best regards,
> Krishna
>
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