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Entry  Fri Aug 22 18:05:02 2014, Andres, Update, IMC, Upgrade of the IMC WFSs for the reflection ModeCleanerUpgrade.PNG
    Reply  Mon Aug 25 09:56:21 2014, Steve, Update, IMC, IMC WFSs upgrade eq6Mnapa.png
    Reply  Tue Aug 26 23:46:55 2014, ericq, Update, IMC, WFS tuneup newWFSmatrix.pdf
       Reply  Wed Aug 27 09:12:47 2014, Koji, Update, IMC, WFS tuneup 
Message ID: 10431     Entry time: Tue Aug 26 23:46:55 2014     In reply to: 10427     Reply to this: 10432
Author: ericq 
Type: Update 
Category: IMC 
Subject: WFS tuneup 

 I decided to see what I could do with the new WFS setup. 

First, I adjusted the WFS digital demod angles. Once I ensured that the static MC alignment and DC alignment onto the WFS was good, I drove MC2 in pitch with the WFS output off. I then did the usual thing of making the Q peak at the excitation frequency go away. Here are the changes:

  • WFS1 Q1: 7 -> -24 (-31)
  • WFS1 Q2: 6.5 -> -9.5 (-16)
  • WFS1 Q3: -6.5 -> -26.5 (-20)
  • WFS1 Q4: 47 -> 30 (-17)
  • WFS2 Q1: -51 -> -39 (-12)
  • WFS2 Q2: -39 -> -21 (-18)
  • WFS2 Q3: -32 -> -20 (-12)
  • WFS2 Q4: -120 -> -108 (-12)

I then drove each MC mirror in pitch and yaw respectively, and measured the TF from excitation to the WFS signal (dB Magnitude, sign):

 

Mirror DoF WFS1 Pitch WFS1 Yaw WFS2 Pitch WFS2 Yaw
MC1 Pit -67.7,+ -81.9,+ -58.9,- -83.7,+
  Yaw -82.5,- -48.7,- -83.7,+ -112.3,-
MC2 Pit -50.4,- -77.1,- -54.2,- -67.9,+
  Yaw -82.1,- -52.9,+ -59.6,- -44.0,-
MC3 Pit -59.7,- -97.3,+ -62.0,+ -83.9,-
  Yaw -78.0,+ -52.9,+ -67.3,+ -51.4,+

 

I looked through some old ELOG's of Suresh's and used similar logic to scripts/MC/WFS/wfsmatrix2.m to generate a new output matrix. (This involves creating a null sensing vector that is orthogonal to the measured ones, and inverting that matrix) 

Old:

Pitch WFS1 WFS2 MC2T   YAW WFS1 WFS2 MC2T
MC1 -1 0.044 0   MC1 -1 -0.294 0
MC2 0.19 1 1   MC2 -0.26 -0.045 -1
MC3 0.5 -0.681 0   MC3 -.9 1 0

 

New:

 

Pitch WFS1 WFS2 MC2T   YAW WFS1 WFS2 MC2T
MC1 0.835 -1 0   MC1 -1 -0.229 0
MC2 -0.948 -0.433 1   MC2 0.317 -1 -1
MC3 -1 0.865 0   MC3 0.743 0.628 0
 

 

I had to flip a gain or two to keep things stable, then measured the WFS error signal spectra to see if this made anything better. The WFS1 spectra look better, but WFS2 not so much. 

newWFSmatrix.pdf

The loops would need a more thorough investigation, but for now, they're at least a little calmer. The MC is stabler than immediately after the upgrade, but there's still room for improvement. 

 

ELOG V3.1.3-