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Entry  Mon Dec 22 15:46:58 2014, Kurosawa, Summary, IOO, Seven transfer functions MC_OLTF.pdf
    Reply  Mon Dec 22 21:53:08 2014, rana, koji, Update, IOO, Seven transfer functions MC_OLG.pdf
       Reply  Tue Dec 23 01:55:35 2014, rana, koji, Update, IOO, Seven transfer functions MC_FSS_TF.pdf
          Reply  Tue Dec 23 20:50:39 2014, rana, koji, Update, IOO, Seven transfer functions MC_OLTF.pdfMC_OLTF2.pdfmatlab.zip
             Reply  Sun Jan 4 22:08:46 2015, rana, Update, IOO, MC loop characterizations: PZT/EOM crossover MC_OLGs.pdfMC_xover.pdf
             Reply  Mon Jan 5 23:36:47 2015, ericq, Update, IOO, AO cable reconnected 
Message ID: 10851     Entry time: Sun Jan 4 22:08:46 2015     In reply to: 10841
Author: rana 
Type: Update 
Category: IOO 
Subject: MC loop characterizations: PZT/EOM crossover 

 * PMC + MC were unlocked when I came in.

* I fiddled around some more with the mcup/down scripts to make locking snappier. The locking was breaking the PMC lock often, so I re-enabled the MC servo board output limiter during acquisition. It is disabled in the MC UP script.

* Re-measured the MC OLG. Still OK.

* Measured the PZT / EOM crossover (aka the FAST / PC crossover) using the connectors on Koji's summing box. With the FAST gain at 18 dB, the crossover is ~10 kHz. Looks way to shallow. Plots to follow.

* I finally discovered today that the PMC PZT stroke is what's causing the main mis-alignment of the beam going to the IMC. By relocking at a few positions, I could see that the IOO QPDs have steps when the PMC relocks. So the IO beam wander is NOT due to temperature effects on the optics mounts of the PSL table. I wonder if we have a large amount of length to angle coupling or if this is the same as the OMC PZTs ?

P.S. I found that someone is using a temporary bench power supply to power the summing box between the TTFSS and the Thorlabs HV driver...whoever did this has ~48 hours to hook up the power in the right way or else Koji is going to find out and lose it and then you have to wear the Mickey Mouse hat.


The first attachment shows the OLG measurements with 2 different values of the fast gain (our nominal FG is 18 dB). You can see that the higher gains produce some crossover instability; when tuning the gain we notice this as an increase in the PCDRIVE rms channel.

The second attachment shows the measurement of the 'crossover'. Its really just the direct measurement of the IN1 / IN2 from the FAST summing box, so its the crossover measurement where the OLG is high.

Attachment 1: MC_OLGs.pdf  39 kB  Uploaded Mon Jan 5 10:49:46 2015  | Show | Show all
Attachment 2: MC_xover.pdf  42 kB  Uploaded Mon Jan 5 11:27:00 2015  | Show | Show all
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