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Entry  Fri Apr 13 03:15:12 2012, koji,frank,tara, DailyProgress, optic, vibration damping on optics IMG_0731.jpgdamped.png
    Reply  Sat Apr 14 06:03:23 2012, frank,tara, DailyProgress, optic, vibration damping on optics IMG_0744.jpgIMG_0742.jpg
       Reply  Mon Apr 16 02:20:58 2012, tara, DailyProgress, optic, vibration damping on optics beat_2012_04_15.pngbeat_2012_04_15.png
          Reply  Mon Apr 16 22:02:08 2012, tara, DailyProgress, optic, vibration damping on optics beat_2012_04_15_fixed.png
             Reply  Wed Apr 18 00:49:07 2012, tara, DailyProgress, optic, vibration damping on optics 
Message ID: 916     Entry time: Mon Apr 16 02:20:58 2012     In reply to: 915     Reply to this: 921
Author: tara 
Type: DailyProgress 
Category: optic 
Subject: vibration damping on optics 

I measured beat signal, after damping most of the optics, realigning the beams to the cavities, measured the slope of error signals and applied it to the measured detection noise.  Acoustics peaks around 200Hz to 1kHz still present.


Fig1: beat measurement, I added shot noise and electronic noise from both cavities to a single trace called detection noise (from measurement).

 I turned off the HEPA fans on the table and on the clean bench before measured the beat signal (after I finished, I turned on the fans as usual).

     The peak at 58 Hz shows up this time. I think this is the peak from beam line motion of the stacks, see PSL:716.  (I think that was before we switched to the softer springs, I'll double check). Note that the air springs were not activated during the measurement, we can try using it and see if there is any improvement.

     There is a good improvement on minimizing the acoustic peaks, although still not enough. Also, increasing the modulation depth seems to help with the flat noise part at high frequency, we may really sit on detection noise.

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