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Entry  Thu Apr 17 01:18:34 2014, Jenne, Update, LSC, Attempt at handing CARM to REFL11 
    Reply  Fri Apr 18 12:53:54 2014, Jenne, Update, LSC, Attempt at handing CARM to REFL11: Time series CARMin1_POPDC_TRX_1000sec_TRXwas1ct.pnglockloss_CARMoscillating.pnglockloss_CARMoscillating_2.png
Message ID: 9821     Entry time: Thu Apr 17 01:18:34 2014     Reply to this: 9829
Author: Jenne 
Type: Update 
Category: LSC 
Subject: Attempt at handing CARM to REFL11 

[Jenne, Koji]

This evening, Koji and I followed the procedure from last night (elog 9817), with the exceptions that as we saw gain peaking in the DARM spectrum, we lowered the DARM servo gain.  We also left the DARM FM4 boost off, and added (TRX+TRY) power normalization to AS55 (although we still had to hand-reduce the gain).    These changes enabled us to reduce the CARM offset much further.  We were able to get the transmitted powers to hold steady at about 1 count while on the IR signals, which is a new record for us.  (We had in the past held the arms with ALS at several counts, but the power fluctuations were huge, and now they are nice and small).

After that, we started looking at whether we could transition CARM over to REFL11I.  We tried a few times, but never made it all the way.


Here are some times for data-foraging tomorrow:

8:27pm, nice transition, CARM offset reduction to 0.6 before lockloss.

9:19pm, turned on power normalization for AS55Q, then reduced CARM offset to 0.5

9:40pm, Lockloss after reducing CARM offset to -0.24, arm transmitted powers around 0.9.

gps 1081748419: First trial trying to transition CARM to REFL11I normalized by (TRX+TRY).

gps 1081749965:  Tried to transition CARM to (REFL11 + REFL33)/(TRX+TRY).  Got about 1/3 of the way through the transition (in terms of matrix element value steps) before lockloss.

11:56pm, Tried to add in REFL11I to CARM error signal (without reducing 1/sqrt(trans) matrix elements).  We increased the REFL11 matrix element until we saw gain peaking, and then tried reducing the 1/sqrt(trans) contribution, and lost lock.  We were only at an offset of 0.3, so we probably weren't close enough to the resonance yet.  We were able to add in REFL11 information, but this was probably not too hard, since there wasn't much actual information in it.


Thoughts:

* It's a little weird that once we are on IR signals, the 0 CARM offset point that we find with ALS is not the true CARM offset point.  Although, this may be because we're just going to an averaged no CARM offset place with ALS, but since ALS is noisy, we won't ever really be holding on the zero offset point.  Anyhow, when we were using the 1/sqrt(trans) signals for CARM, and the CARM digital offset was -0.24, the ALSX and ALSY outputs were both about 0.5 in magnitude.

* We're getting there! 

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