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Entry  Thu Oct 17 16:49:53 2019, gautam, Update, ASC, PRMI ASC - first pass PRMI_ASC.pdf
    Reply  Tue Oct 22 17:35:30 2019, gautam, Update, ASC, PRMI ASC - first pass originalPOP_QPD.pngPOP_QPD_modified.png
       Reply  Wed Oct 23 11:14:21 2019, gautam, Update, ASC, PRMI ASC with QPD signals normalized. PRMI_ASC_normalization.pdfPRMI_ASC_Oct22.pdf
Message ID: 14988     Entry time: Wed Oct 23 11:14:21 2019     In reply to: 14985
Author: gautam 
Type: Update 
Category: ASC 
Subject: PRMI ASC with QPD signals normalized. 

Attachment #1 - comparison of the POP QPD PIT and YAW output signal spectra with and without them being normalized by the SUM channel. I guess the shape is different between 30-100 Hz because we have subtracted out the correlated singal due to RIN?

This did not have the effect I desired - I was hoping that by normalizing the signals, I wouldn't need to change the gain of the ASC servo as the buildup in the PRC changed, but I found that the settings that worked well for PRMI locked with the carrier resonant (no arm cavities, see Attachment #2, buildup RIN reduced by a factor of ~4) did not work for the PRMI locked with the sideband resonant. Moreover, Koji raised the point that there will be some point in the transition from arms off resonance to on resonance where the dominant field in the PRC will change from being the circulating PRC carrier to the leaking arm carrier. So the response of the actuator (PRM) to correct for the misalignment may change sign. 

In conclusion, we decided that the best approach to improve the angular stability of the PRC will be to revive the PRC angualr feedforward, which in turn requires the characterization and repair of the apparently faulty vertex seismometer.

Attachment 1: PRMI_ASC_normalization.pdf  63 kB  Uploaded Wed Oct 23 12:15:39 2019  | Hide | Hide all
Attachment 2: PRMI_ASC_Oct22.pdf  134 kB  Uploaded Wed Oct 23 12:22:59 2019  | Hide | Hide all
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