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Entry  Tue May 26 02:15:36 2020, gautam, Update, LSC, Lock acquisition portal entry 
    Reply  Tue May 26 02:31:00 2020, gautam, Update, LSC, Lock acquisition sequence PRFPMIlock_1274418200_1274418550.pdf
       Reply  Wed May 27 20:14:51 2020, Koji, Update, LSC, Lock acquisition sequence 
    Reply  Tue May 26 02:37:19 2020, gautam, Update, LSC, DARM loop measurement and fitting DARM_TF.pdfDARM_TF_breakdown.pdf
    Reply  Tue May 26 03:01:35 2020, gautam, Update, LSC, CARM loop  CARM_OLTF.pdf
       Reply  Wed Jun 3 01:46:14 2020, gautam, Update, LSC, CARM loop  CM_loop_topology.pdfCARM_TFs.pdfCARM_OLTF.pdfCARM_xover.pdfCARM_OLG_evolution.pdf
    Reply  Tue May 26 03:06:59 2020, gautam, Update, LSC, PRFPMI sensing matrix PRFPMI_20200524sensMat.pdfPRFPMI_20200524sensMatHistograms.pdf
    Reply  Tue May 26 03:26:58 2020, gautam, Update, LSC, Preliminary noise budget PRFPMI_NB.pdf
    Reply  Tue May 26 14:32:44 2020, gautam, Update, LSC, Arm transmission RIN armRIN.pdf
       Reply  Wed May 27 19:36:33 2020, Koji, Update, LSC, Arm transmission RIN 
          Reply  Thu May 28 18:36:45 2020, gautam, Update, LSC, Arm transmission RIN PRFPMIcorner_ASC_PIT_1274419354_1274419654.pdfPRFPMIcorner_ASC_YAW_1274419354_1274419654.pdfPRFPMIcorner_ASC_coherence_1274419354_1274419654.pdf
             Reply  Fri May 29 00:34:57 2020, rana, Update, LSC, Arm transmission RIN 
             Reply  Wed Jun 3 02:14:32 2020, gautam, Update, ASC, PRC ASC improves arm transmission RIN PRC_ASCsignals.pdfarmRIN_PRC_ASC.pdfPRFPMIcorner_ASC_PIT_1275190251_1275190551.pdfPRFPMIcorner_ASC_YAW_1275190251_1275190551.pdfPRFPMIcorner_ASC_coherence_1275190251_1275190551.pdf
                Reply  Fri Jun 19 16:30:09 2020, gautam, Update, ASC, Some thoughts about ASC sensingResponse.pdfsensingResponse_torque.pdf
                   Reply  Tue Jul 7 14:06:10 2020, gautam, Update, ASC, Some more thoughts about ASC ITM_OL_DCcoupling.png
    Reply  Tue May 26 16:00:06 2020, gautam, Update, LSC, Power buildup diagnostics PRFPMIcorner_DC_1274419354_1274419654.pdfPRFPMIcorner_SB_1274419354_1274419654.pdf
       Reply  Wed May 27 17:41:57 2020, Koji, Update, LSC, Power buildup diagnostics 
          Reply  Wed Jun 3 02:08:00 2020, gautam, Update, LSC, Power buildup diagnostics PRFPMIcorner_DC_1275190251_1275190551.pdfPRFPMIcorner_SB_1275190251_1275190551.pdf
    Reply  Wed Jun 3 01:34:53 2020, gautam, Update, LSC, Lock acquisition update portal 
       Reply  Wed Jun 3 03:29:26 2020, Koji, Update, LSC, Lock acquisition update portal 
          Reply  Wed Jun 3 11:40:56 2020, gautam, Update, LSC, Lock acquisition update portal 
             Reply  Wed Jun 3 18:49:47 2020, gautam, Update, LSC, PRG and CARM signal sign armCavReflectivities.pdfIFOreflectivities.pdfPDHerrSigs.pdfPRGvsLoss_finesse.pdf
Message ID: 15361     Entry time: Thu May 28 18:36:45 2020     In reply to: 15359     Reply to this: 15362   15368
Author: gautam 
Type: Update 
Category: LSC 
Subject: Arm transmission RIN 

I agree, I think the PRC excess angular motion, PIT in particular, is a dominant contributor to the RIN. Attachments #1-#3 support this hypothesis. In these plots, "XARM" should really read "COMM" and "YARM" should really read "DIFF", because the error signals from the two end QPDs are mixed to generate the PIT and YAW error signals for these ASC servos - this is some channel renaming that will have to be done on the ASC model. The fact that the scatter plot between these DoFs has some ellipticity probably means the basis transformation isn't exactly right, because if they were truly orthogonal, we would expect them to be uncorrelated?

  • In the corner plots, I am plotting the error signals of the ASC servos and the arm transmission. POP feedback is not engaged, but some feedback control to the ETMs based on the QPD signals is engaged.
  • In the coherence plot, I show the coherence of the ASC error signals with the POP and TR QPD based error signals, under the same conditions. The coherence is high out to ~20 Hz.

I guess what this means is that the stability of the lock could be improved by turning on some POP QPD based feedback control, I'll give it a shot.

Quote:

- PRC TT misalignment (~3Hz)

Don't can you check the correlation between the POP QPD and the arm RIN

Attachment 1: PRFPMIcorner_ASC_PIT_1274419354_1274419654.pdf  636 kB  Uploaded Thu May 28 19:40:33 2020  | Hide | Hide all
PRFPMIcorner_ASC_PIT_1274419354_1274419654.pdf
Attachment 2: PRFPMIcorner_ASC_YAW_1274419354_1274419654.pdf  716 kB  Uploaded Thu May 28 19:40:45 2020  | Hide | Hide all
PRFPMIcorner_ASC_YAW_1274419354_1274419654.pdf
Attachment 3: PRFPMIcorner_ASC_coherence_1274419354_1274419654.pdf  194 kB  Uploaded Thu May 28 21:55:36 2020  | Hide | Hide all
PRFPMIcorner_ASC_coherence_1274419354_1274419654.pdf
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