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Entry  Thu Mar 7 18:12:03 2013, yuta, Update, Alignment, Input beam drift ~ 0.1 mrad/h in pitch IPangulardrift.png
    Reply  Fri Mar 8 20:51:00 2013, Manasa, Update, Alignment, Input beam drift - investigation **IMPORTANT** 
       Reply  Mon Mar 11 12:29:25 2013, Manasa, Update, Alignment, Input beam drift - weekend trend IPANG_drift.png
          Reply  Tue Mar 12 14:02:22 2013, Jenne, Update, Alignment, Beam drift - mystery partially solved? 
Message ID: 8267     Entry time: Mon Mar 11 12:29:25 2013     In reply to: 8262     Reply to this: 8279
Author: Manasa 
Type: Update 
Category: Alignment 
Subject: Input beam drift - weekend trend 

I centered ipang and ippos on the QPDs (using only the steering mirrors) and wanted to see the drift over the weekend.

1. IPANG has drifted (QPD sum changed from -6 to -2.5); but it is still on the QPD.
2. IPPOS does not show any drift.
3. In the plot: The jump in IPANG on the left occured when I centered the beam to the QPD and that on the right is from the 4.7 earthquake and its aftershocks this morning.

Follow-up questions
1. Do we need to worry about this drift?
2. Which of the two TTs is resposible for the drift?
3. Do the TTs tend to drift in the same direction everytime?

P.S. The TTs were not touched to center on IPANG and IPPOS. The last time they were touched was nearly 6 hours before the centering. So the question of any immediate hysteresis is ruled out.


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