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Entry  Mon May 7 12:57:34 2012, Den, Update, IOO, WFS noise in MC gur_suspos_coh.pngmc1_gur.pngmcl_wfs.pngwfs_servo.png
    Reply  Mon May 7 17:28:29 2012, Den, Update, IOO, WFS noise in MC wfs_limit.png
       Reply  Mon May 7 19:39:52 2012, Koji, Update, IOO, WFS noise in MC 
          Reply  Mon May 7 20:15:37 2012, Den, Update, IOO, WFS noise in MC 
Message ID: 6612     Entry time: Mon May 7 12:57:34 2012     Reply to this: 6613
Author: Den 
Type: Update 
Category: IOO 
Subject: WFS noise in MC 

I've measured coherence between seismometer signals and OSEMS of MC 1,2,3

gur_suspos_coh.png

GUR1 was rotated on the angle pi / 4 relative to x arm to match suspos axis of MC1 and MC3. Coherence between MC2 and GUR2_X is high, between MC3 and GUR1_X is ~0.2 but is compensated by GUR1_Y, between MC1 and GUR1_Y below 1Hz is ~0.5 and is not compensated by GUR1_X.

Then I measured coherence between GUR1_Y and MC3 OSEMS in 3 regimes :

  • FEEDBACK OFF, WFS OFF
  • FEEDBACK ON, WFS OFF
  • FEEDBACK ON, WFS ON

mc1_gur.png

Once WFS are ON, signal becomes noisy, FEEDBACK is OK. Then I measured coherence between MC_F and GUR2_X with WFS ON and OFF

mcl_wfs.png

Coherence between MC_F and GUR2_X is less when WFS are ON in the range 0.2 - 1 Hz and 4 - 10 Hz. Moreover PSD of MC_F seems to be higher at 10 - 100 Hz. But this may be caused by other reasons.

Then I measured the coherence between IN and OUT signals in WFS_SERVO

wfs_servo.png

One filter bank adds noise to WFS signals and because of that we loose coherence between MC_F and seismic motion.

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