Page History

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• We created geometry files for both cspad2x2 and cspad using TJ's psgeom converters from the crystfel .geom files
• The z-position of the cspad was determined by the crystfel geoptimiser.  This also places the sample position at the origin.
• The z-position of the cspad2x2 was measured by Andy Aquila with a tape measure to be 2.4m +- few mm.
• The origin of the cspad2x2 was set by looking at the rings in one of the "good hit" events provided by the uppsala group (image below)
• We then looked at the picture of both detectors below.
  
  • Andy said for the cspad2x2 up is toward the left.  At LCLS "up" corresponds to positive-y, so this should go to the right.
  • Given that the cspad has positive-y toward the right we need to rotate the cspad2x2 by 180 degrees.  A flip would be incorrect, because it would change the "handedness" of the big cspad shadow seen on the little cspad
  • The above 180 degree rotation is consistent with Andy's picture that the cspad2x2 streak going towards the left corresponds to the cspad bright streak going toward the right.
  • cpo noticed that the shadow gap between the two 2x1's is about the same size on both pictures.  this implies the shadow is not being created by a point at the sample position (if that was true the back image would be 4 times as large as the front).  Andy confirmed that this was likely a diamond window 1 or 2 meters upstream from the sample that was glowing.

Image used to determine that we needed to rotate cspad2x2 by 180 degrees around z:

Rings used to set x/y origin of cspad2x2 coordinate frame (location of sample):

After rotating the cspad2x2 by 180 degrees around z we obtain the following "final" images:

Image Added