The coils move radially inward when they are powered, something like 7-10
mm. The detector subframe stays fixed. The coils are also not in their
ideal positions/angles, but hopefully that's a small effect on the
with/without shielding difference. If anything, using the true coil radial
position probably REDUCES the with/without shielding difference.
Karen
At 10:03 AM 5/18/2005 -0400, Douglas Hasell wrote:
>Hi Eugene,
>
> As I understand things the agreement at forward angles is quite
>good. Where the reconstruction has problems is around 40-50 degrees
>and with softer momenta say 500-600 MeV. If you could simulate a
>track like that it would be useful.
>
> The other effect I wanted to ask is whether or not you are using
>the ideal positions for the BLAST coils or if you were able to get
>the actual positions which are shifted by about 10 mm?
>
>
>
>
> 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
>
>On May 13, 2005, at 7:47 PM, Eugene J. Geis wrote:
>
>>.... Don't know what happened with the files... One more time
>>with the old
>>message.....
>>
>>The file "Contour Field and Trajectory.png" is an overhead view of
>>the field in
>>the ZX BLAST frame. It is a contour map of the field. There is a
>>blue line
>>that represents a simulated electron's trajectory that came out of
>>the origin
>>at a polar angle of 25 degrees and energy 850 MeV.
>>
>>The track has been simulated but stepping 1 cm at a time 350 times
>>through the
>>field. The file "Electron_Track_Mag.ps" is 2 plots of the
>>deviation of the
>>exact same particle, i.e. same initial conditions, at each step in "No
>>Shielding" and "Shielding" situations. The deviations plotted are
>>the overall
>>magnitude difference of the position at each step and the overall
>>magnitude
>>difference of the momentum at each step. The maximum deviation
>>proves to be
>>0.16 cm at a point outside the field and approximate 2.3 MeV
>>different at the
>>exit from the field. This is well below our extracted offsets and
>>momentum
>>resolution.
>>
>>There are also three plots included which are plots of the Flux
>>Density in the
>>Y direction. They are labeled as "Field_to_CC0_Done.ps",
>>"Field_to_CC1_Done.ps", and "Field_to_CC2_Done.ps". The fields in
>>these three
>>plots have been plotted along a line stretching from the origin to
>>the center
>>of
>>the three respective Cerenkov boxes. In each file, there are two
>>plots. The
>>plot on the left is a superposition of the field simulations with
>>(in blue) and
>>without shielding (in red). On the right, the ratio at accessible
>>bins is
>>plotted (Shielded divided by NOT Shielded). The x-axis is the
>>length over the
>>path of our plot in centimeters (the path from the origin to the CC
>>box). Some
>>of the deviations in the first 100 centimeters of each plot may be
>>results of
>>the Finite Element meshing or they may be real. Either way, at the
>>deepest
>>center of our field, the ratio never seems to differ by more than
>>2%. There is
>>a consistent dip in each as you approach the CC boxes but the field
>>is rapidly
>>approaching zero as this dip becomes more pronounced and this will
>>not affect
>>our reconstruction since the electron would have already punched
>>through the
>>WC's at this point.
>>
>>
>>In conclusion, TOSCA shows no major deviation that would come close
>>to the
>>kinematical problems in reconstruction. Within the first 200 cm's
>>along the
>>simulated path of an 850 MeV electron (slightly higher than what is
>>actually
>>there, my apologies...), we remain within the width of our 200 micron
>>resolution in the WC's.
>>
>>Michael suggested attempting to corroborate the present field map
>>with new
>>TOSCA calculations. I would like to know what the format of the
>>field map is
>>and where to find it. I can resume working on something like this
>>in about 3
>>weeks when I'm done with the stress of moving and feeling settled
>>back in
>>Arizona. That is, as long as Ricardo has purchased the program...
>>
>>I'm leaving on Monday. Hope to see you all again at the next
>>collaboration
>>meeting.
>>
>>eugene
>>
>>
>>---------------------------------------------------------------------- ----
>>Eugene Geis
>>PhD Student, Physics Department, ASU
>>Research Affiliate, MIT-Bates Laboratory of Nuclear Science
>>eugene.geis@asu.edu
>>
>>----- End forwarded message -----
>>
>>
>>
>>---------------------------------------------------------------------- ----
>>Eugene Geis
>>PhD Student, Physics Department, ASU
>>Research Affiliate, MIT-Bates Laboratory of Nuclear Science
>>eugene.geis@asu.edu
>>---------------------------------------------------------------------- ----
>>http://quickreaction.blogspot.com
>>
>><Contour Field and Trajectory.png>
>><Electron_Track_Mag.ps>
>><Field_to_CC0_Done.ps>
>><Field_to_CC1_Done.ps>
>><Field_to_CC2_Done.ps>
>
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