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Entry  Tue Nov 19 21:28:05 2013, manasa, Update, LSC, PRMI carrier locking 
    Reply  Tue Nov 19 21:59:35 2013, manasa, Update, LSC, PRMI carrier locking 
       Reply  Wed Nov 20 01:10:38 2013, Jenne, Update, LSC, PRMI carrier locking 
          Reply  Wed Nov 20 16:05:52 2013, Jenne, Update, LSC, PRMI carrier locking, OpLev Check 
Message ID: 9416     Entry time: Wed Nov 20 01:10:38 2013     In reply to: 9415     Reply to this: 9417
Author: Jenne 
Type: Update 
Category: LSC 
Subject: PRMI carrier locking 

I have increased the gain of the MICH loop to -100, and set FMs 2,3,7 to be triggered.  I have also increased the PRCL gain to 2.  The PRCL ASC pitch and yaw gains used to be -0.004, but I have increased them both to -0.01.

Now, I'm seeing power fluctuations in POPDC of ~200 pk-pk, at an average value of 2650.  That's a RIN of 7.5% .  If I turn off all OSEM damping for the PRM (after the cavities are already locked), I get POP DC fluctuations of 100 pk-pk at the same average value, so a RIN of 4%. 

Back on October 30th (elog 9338), we had an average POPDC of 400, with fluctuations of 200 pk-pk, so a RIN of 50%. 

So, I am pleased that, with the carrier locking, I have lower power fluctuations.  And, since there is more overall power in the PRC right now than we had 3 weeks ago, I'm hopeful that a PRMI+arms test will have lower power fluctuation.

Also, a note, when my MICH gain was still low, I had lots of power fluctuation at the AS port, which was coherent with my POPDC power fluctuations (which makes sense).  At that time, my overall RIN was higher than it is now (although I neglected to write down the numbers), but more significantly, I saw occasional 'kicks', where the ASDC and POPDC powers would ring for 1 or 2 seconds, with power fluctuations of order 40%.  I have not seen any of those kicks since increasing the MICH gain.

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