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Entry  Tue Oct 20 15:51:44 2015, ericq, Update, SUS, MC2 F2P tuned 
    Reply  Fri Oct 23 21:58:10 2015, rana, Update, SUS, MC2 F2P mis-tuned 
       Reply  Tue Oct 27 03:46:26 2015, ericq, Update, SUS, MC2 F2P mis-tuned 
Message ID: 11702     Entry time: Tue Oct 20 15:51:44 2015     Reply to this: 11711
Author: ericq 
Type: Update 
Category: SUS 
Subject: MC2 F2P tuned 

Using a modified version of Hang's deMod_deCoup scripts, I tuned the MC2 coil output matrix to minimize the appearance of POS drive in the SUSPIT signal at 28Hz. Up until now, there was no F2P compensation. This reduced the force to pitch coupling at 28Hz by 8dByes

Old: POS -> 1 x UL, 1 x UR, 1 x LL, 1x LR

New: POS -> 1.1054 x UL, 1.1054 x UR, 0.8946 x LL, 0.8946 LR

I checked the MCL spectrum before and after this change with OAF on, this did not spoil the feedforward length subtraction in any noticible way. 

The script lives in userapps/release/isc/c1/scripts/decoup, but I've symlinked it to /opt/rtcds/caltech/c1/scripts/decoup.


The script modification I made had to do with how the I and Q data is collected. Before, it was sporadically probing the I and Q FM output monitor EPICS values; I changed it to use the avg function of cdsutils, which calculates the mean and std from the 16kHz data and have seen it improve results by 1dB or so. I've been in touch with Jenne to propagate this to the sites. 

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