[PRad] [Revised Logentry] Y axis shift in calibration scan and Re-start from the 3rd row of Cyrstal modules

[cpeng at jlab.org]

Comments:
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 - by pasyuk on Sun, 05/29/2016 - 12:03.

One should monitor encoders - One should monitor encoders all the time when HyCal is moving. They tell if it actually moves or not. This way you will spot a problem right away.

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Logentry Text:
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I found the Y axis is shifted when I came in the morning, and I checked all the data we have taken in the OWL shift.
The problem is, some times the HyCal is not moving in Y axis, so we stay at the same row for some runs.

Attached spread sheet shows the shift we found in data, here they are some information about the spread sheet:
G means lead glass module, W means crystal module (lead tungstate).
We planned to scan 6 G rows in the top set of lead glass modules, and then go to W rows (crystal module).
G module size is 3.82 cm and W module size is 2.05 cm.

In summary, finally we got 16 cm shift in Y position.
It seems HyCal does not move in Y some times. Thus we missed the first 6 modules in 5th G and 6th G rows since the program thought it was scanning W rows.
Currently we don't know if it is the bug in moving program or there is some thing blocking HyCal (less likely).
Thus RC decided to re-start at 3rd W row and carefully monitor the scan for several rows.
We will scan the missing modules G121 - G126 and G151-G156 when we scan for the bottom left set of lead glass.


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