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User name mcnulty
Log entry time 12:32:57 on August29,2009
Entry number 286823
This entry is a followup to: 286469
keyword=Rarm alignment analysis update
Here is a re-analysis of run 4351 (Thick Ta Spectra) in which I project the tracks to the plane of the detector (approximately 0.5 meters above the VDC1 plane). The bottom left plot shows outline of the detector. The bottom right plot shows the ADC signal attenuation slope; from this I interpret the edge of the active part of the detector at x = 1.2 m and the photocathode is 4 or 5 cm beyond this (at x = 1.25 m).
Figure 2 is from run 4382 (H2 target at 1uA). One can see the outline of the hapdet--the rotation seems fine, however as mentioned before, the detector should be moved in neg y direction about 2cm. From the attenuation slope plot it seems the super-elastic edge is in a good position at about 25 - 30cm from the pmt cathode.