[PRad] target center

[Maxime Levillain]

Dear colleagues,

Kelly Tremblay checked the survey values for the target since we saw some discrepancies when looking at physics events.
Here is his answer:
"I checked the fiducialized data from 2015/2016 and verified that the survey team used the center of the chamber for the reference 0,0,0 point for the prad target. This places the coordinates shown in memo B1718 being 88.9 mm downstream from the referenced Z location. I am not going to change the memo or are target data, but have put flags in the data to show the target cell is downstream 88.9 for future reference. The true Z found coordinate position of the target is -385.73294.
Hope this clears this up.
Kelly"

This new value should clear out the discrepancy that we found in the study.

Maxime