40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log  Not logged in ELOG logo
Entry  Tue Oct 27 03:56:52 2015, ericq, Update, LSC, DRFPMI work 
    Reply  Thu Oct 29 03:25:49 2015, ericq, Update, LSC, DRFPMI work DRFPMI.pdfDRMIarms.pdf
       Reply  Tue Nov 3 03:12:46 2015, ericq, Update, LSC, DRFPMI work 
Message ID: 11726     Entry time: Tue Nov 3 03:12:46 2015     In reply to: 11722
Author: ericq 
Type: Update 
Category: LSC 
Subject: DRFPMI work 

Tonight was kind of a wash. 

We spent some time retaking single arm scans with Gautam's frequency counting code to confirm the linewidths he measured before his most recent round of code improvements. During this, ETMX was being its old fussy self, costing us gentle realignment time. For the time being, we started actuating on ITMX for single arm locks. Also, out of superstition, I changed the static position offset that had been at +1k for the last N months to -1k. 

ETMX broke us out of a few DRFPMI lock trials as well, as did poor SRM alignment. I finally set up dither alignement settings for SRM in DRMI though, which helped (even in the arms-held-off-resonance situation). I still prefer doing the PRM/BS dither alignment in a carrier PRMI lock, because I think the SNR should be better than DRMI. 

We know that the ETMX excursions can happen without length drive exciting them, but also that length drives certainly can excite them. For future locks, I'm going to try out avoiding ETMX drive altogether; the sites use a single ETM for their DARM actuation and let the CARM loop take care of the resultant cross coupling, so hopefully we can do the same without angering the mode cleaner.

Anyways, we didn't really ever make it far enough to do anything interested with the DRFPMI tonight frown

ELOG V3.1.3-