The old bgrid2.blast was SUPPOSED to be the real measured fields;
we didn't realize it was really Biot-Savart until 3 months ago. Is there
already a bgrid.blast that is the Biot-Savart? I agree, you want to keep
an ideal B-S around for comparison, but I think it might already be there
as bgrid.blast.
Karen
At 12:49 PM 10/5/2005 -0400, Michael Kohl wrote:
>Chris,
>
>the old bgrid2.blast was based on Biot-Savart calculations, while the new
>one is based on the measured field map. This is not just a bugfix. It
>would be good to have both maps with different filenames checked in.
>Especially if one wants to directly compare results from the two maps, it
>is better to have them both in BLAST_PARAM directory rather than having to
>modify the checked-out cvs directory. So please, either give the new map
>another name or rename the old map to bgrid2_bs.blast (Biot-Savart) or so!
>
>Regards,
>
> Michael
>
>
>
>On Wed, 5 Oct 2005, Chris Crawford wrote:
>
> > Michael,
> > I checked in the larger bgrid as its own filename, but kept the new
> > smaller one as bgrid2.blast, since it really is a fix. You can always
> > check out previous versions as different names.
> > --Chris
> >
> > Michael Kohl wrote:
> > > Hi Chris,
> > >
> > > please give the large map a different name that will be specified in
> > > .blastrc. Also, Doug's new map should be bgrid3.blast. Different
> versions
> > > in CVS with the same filename are only justified if there are
> bugfixes to
> > > an existing map.
> > >
> > > Regards,
> > >
> > > Michael
> > >
> > >
> > >
> > > On Tue, 4 Oct 2005, Chris Crawford wrote:
> > >
> > >
> > >>Hi Doug,
> > >> I copied the file to
> > >>/home/daq/blast/pro2004/Blast_Params/bgrid2.blast, and checked it in
> > >>(version 1.9). Note that cvs_v3/Blast_Params is not used, and also the
> > >>'2' in bgrid2.blast, and #2 in the first line refer to the file format,
> > >>not version of the map. I also fixed the first line.
> > >> I started 'setenv ANALDIR test-2005-10-04; lrn +SQL 12144' from the
> > >>blast acct to test the new field.
> > >> We can either check the larger map as a new version of bgrid2.blast,
> > >>or with a new name like 'bgrid2.large', making it easier to switch back
> > >>and forth. Which do you think would be better?
> > >>--Chris
> > >>
> > >>
> > >>Douglas Kenneth Hasell wrote:
> > >>
> > >>>Hi,
> > >>>
> > >>> I have put a file "bgrid3.blast" into the Blast_Params sub-
> > >>>directory of the blast account. I have not done anything else
> and hope
> > >>>someone who knows what they are doing can take the appropriate action.
> > >>>
> > >>> This file has the same ranges (ie size) as the previous grid files
> > >>>so no changes are needed to the code other than whatever is necessary
> > >>>to have the field calculating code point at this file rather than
> > >>>bgrid2.blast.
> > >>>
> > >>> The new file "bgrid3.blast" is based on the field mapping
> data from
> > >>>Abby Goodhue "TOT.dat". I used her results but edited to remove any
> > >>>point which differed by more than 200 G from the Biot-Savard
> > >>>calculation (this had the effect of removing about 150 bad points). I
> > >>>then fit the mapped data allowing the coils to move and obtained a
> > >>>good fit with R = -8.1 mm, Z = 8.09 mm, and some small angle changes.
> > >>>
> > >>> I then filled the desired grid with the closest mapped result if
> > >>>one existed and with the offset coil calculated result if no mapped
> > >>>data was close. If the calculated point is greater than 4000 G (which
> > >>>can happen close to the coils) I fix its magnitude to 4000 G to reduce
> > >>>the non-linearities near the coil. Then, since the mapped values are
> > >>>not exactly on the grid points I loop over the grid points and
> > >>>determined the field at the grid point by fitting a second order
> > >>>polynomial in x, y, and z to the 27 points surrounding the
> desired grid
> > >>>point. I do this so long as at least one point of the 27 was a
> > >>>measured value. If all 27 are calculated there is no need to do
> the fit.
> > >>>
> > >>> I am now calculating a new grid following the same procedure as
> > >>>above but changing the ranges so that the grid extends to the TOF's in
> > >>>x, y, and z and also extends back to Z = -1.2 m to include the BAT's
> > >>>
> > >>> The old range was
> > >>>
> > >>> -200 <= x <= 200
> > >>> -70 <= y <= 70
> > >>> -10 <= z <= 290
> > >>>
> > >>> The new range I am calculating now is:
> > >>>
> > >>> -250 <= x <= 250, 101 grid steps
> > >>> -90 <= y <= 90, 37 grid steps
> > >>> -120 <= z <= 380, 101 grid steps
> > >>>
> > >>> For comparison the y component of the field at
> > >>>
> > >>> x = 200, y = 0, z = 0 is -454 G
> > >>> x = 250, y = 0, z = 0 is -95 G (near face of back angle TOF)
> > >>>
> > >>> x = 130, y = 0, z = 290 is -269 G
> > >>> x = 130, y = 0, z = 380 is 10 G (near face of forward angle TOF)
> > >>>
> > >>> This new grid will be approximately 2.6 times larger. If anyone
> > >>>thinks this too large please let me know.
> > >>>
> > >>>
> > >>>
> > >>> Cheers,
> > >>>
> > >>> Douglas
> > >>>
> > >>>26-415 M.I.T.
>
> > >>>Tel: +1 (617) 258-7199
> > >>>77 Massachusetts Avenue Fax: +1 (617)
> > >>>258-5440
> > >>>Cambridge, MA 02139, USA E-mail:
> > >>>hasell@mit.edu
> > >>
> > >>
> > >
> >
> >
>
>--
>
>+-------------------------------------+--------------------------+
>| Office: | Home: |
>|-------------------------------------|--------------------------|
>| Dr. Michael Kohl | Michael Kohl |
>| Laboratory for Nuclear Science | 5 Ibbetson Street |
>| MIT-Bates Linear Accelerator Center | Somerville, MA 02143 |
>| Middleton, MA 01949 | U.S.A. |
>| U.S.A. | |
>| - - - - - - - - - - - - | - - - - - - - - -|
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>| http://blast.lns.mit.edu | |
>+-------------------------------------+--------------------------+
>
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