To tie up some loose ends, I went back to the EY drift event of 07/19/2013 00:00 UTC (elog 7146), which was triggered by turning off the clean room.

The attached plot 1 shows 20 days around the event. Marked in dark blue is the turn-off event, marked in bright clue is the turning on of the same clean room a day after. I am not sure where exactly the two temperature sensors are located, but I amsure the actual temperature jump at the BSC was bigger (From John's elog 7149 is was >2degF).

According to the OSEMS the TMSY drifted by about 5 urad in pitch and yaw (ignore sharp steps due to realignments) - I don't think that can be responsible for us falling off the photodiode. so something else must have moved.

The ETMY is even less: ~2urad in pitch and nothing significant in yaw (plot 2).

The PZT actuators (under QPD control, slaving the beam to the TMS) show some shift, but nothing that would be very unusual.

So the bottom line is: I still don't understand why we fell of the diodes on ISCTEY that day.

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