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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: 9415     Entry time: Tue Nov 19 21:59:35 2013     In reply to: 9414     Reply to this: 9416
Author: manasa 
Type: Update 
Category: LSC 
Subject: PRMI carrier locking 

Quote:

Since we have never tried to lock PRMI on carrier after the folding mirrors were flipped, I tried to lock PRCL on carrier.

I thought this might give us some idea about the PRC stability for resonance or some clue as to what happens to the PRM suspensions and PRMI stability when we have carrier resonating in the cavity.

I changed the sign of the PRCL gain and also tried increasing the gain. But this did not work and I was not able to carrier lock PRMI. May be I am missing to change some parameter that is very trivial?

PRMI could not be locked on carrier using 3f. The configuration from the last time when PRMI was carrier locked (elog) were used and PRMI locked on carrier with these settings.

== PRMI carrier ==
  MICH: AS55_Q_ERR, AS55_PHASE_R = -12 deg,  MICH_GAIN = -0.2, feedback to ITMX(-1),ITMY(+1)
  PRCL: REFL55_I_ERR, REFL55_PHASE_R = 70 deg, PRCL_GAIN = 1.0, feedback to PRM

Below is the video capture showing the PRM front and back face when carrier flashes with few second locks.

EDIT by JCD:

The demod phase numbers that Manasa is quoting above were correct back in March, when the elog she's quoting from was written.  They are not true now, since we've adjusted things in the last 8 months.  Also, I'm using a gain of -1.5 for MICH, and +1.5 for PRCL.  MICH has no FMs triggered, PRCL has FM 2,3,6 triggered.  Since we won't be using this configuration for full locking, but just for some tests, I'm currently using AS55 Q for MICH, and REFL 55I for PRCL, and using the ITMs to actuate on MICH for today.

ELOG V3.1.3-