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Entry  Fri Sep 30 05:35:42 2011, kiwamu, Update, LSC, length fluctuations in MICH and PRCL noise.png
    Reply  Fri Sep 30 08:40:02 2011, Koji, Update, LSC, length fluctuations in MICH and PRCL 
    Reply  Sat Oct 8 04:41:07 2011, kiwamu, Update, LSC, length fluctuations in SRCL length_noise.png
       Reply  Mon Oct 10 10:14:43 2011, rana, Update, LSC, length fluctuations in SRCL 
Message ID: 5638     Entry time: Sat Oct 8 04:41:07 2011     In reply to: 5582     Reply to this: 5641
Author: kiwamu 
Type: Update 
Category: LSC 
Subject: length fluctuations in SRCL 

For a comparison, the length fluctuation of Signal-Recycled ITMX (SRX) and ITMY (SRY) have been measured.

Roughly speaking the length motion of SRX and SRY are as loud as that of PRCL.

Some details about the measurement and data analysis can be found in the past elog entry (#5582).

In the process of converting the raw spectra to the calibrated displacements the SRM actuator was assumed to have a resonance at 1Hz with Q = 5.

length_noise.png

(Notes on SRX/Y locking)

     Sensor = REFL11_I
     Actuator = SRM
     Demod. phase = 40 deg
     SRCL_GAIN = 20
     UGF = 100 - 200 Hz
     Resonant condition = Carrier resonance
     Whitening gain = 0 dB
     ASDC = 360 counts

Quote from #5582

The MICH and PRCL motions have been measured in some different configurations.

      + PRCL is always noisier than MICH.

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