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Entry  Fri May 15 17:30:00 2009, rob, Update, LSC, arms, coils, locks armslock_no_int.png
    Reply  Sat May 16 16:20:33 2009, rob, Update, LSC, arms, coils, locks, #2 twoproblems.pngcoil_imbalanceETMY.pngITMXalignment.png
Message ID: 1592     Entry time: Sat May 16 16:20:33 2009     In reply to: 1591
Author: rob 
Type: Update 
Category: LSC 
Subject: arms, coils, locks, #2 


This is the two arms locked, for an hour.  No integrator in either loop, but from this it looks like ETMY may have a bigger length2angle problem than ETMX.  I'll put some true integrators in the loops and do this again.



 There appear to be at least two independent problems: the coil balancing for ETMY is bad, and something about ITMX is broken (maybe a coil driver). 

The Y-arm becomes significantly misaligned during long locks, causing the arm power to drop.  This misalignment tracks directly with the DC drive on ETMY.  Power returns to the maximum after breaking and re-establishing lock.

ITMX alignment wanders around sporadically, as indicated by the oplevs and the X-arm transmitted power.  Power returns to previous value (not max) after breaking and re-establishing lock.

Both loops have integrators.

Attachment 1: twoproblems.png  25 kB  | Hide | Hide all
Attachment 2: coil_imbalanceETMY.png  18 kB  Uploaded Sat May 16 17:24:39 2009  | Hide | Hide all
Attachment 3: ITMXalignment.png  27 kB  Uploaded Sat May 16 17:26:29 2009  | Hide | Hide all
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