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Entry  Tue Oct 11 03:35:16 2011, kiwamu, Update, LSC, BS actuator reponse at low frequency : measured BSactuator.png
    Reply  Tue Oct 11 15:14:50 2011, rana, Update, LSC, BS actuator reponse at low frequency : measured 
       Reply  Tue Oct 11 19:11:25 2011, kiwamu, Update, LSC, Re: BS actuator reponse at low frequency : measured 
    Reply  Wed Oct 12 17:53:01 2011, kiwamu, Update, LSC, BS actuator response : fitting done and histroy of delays bode_BSactuator.png
Message ID: 5648     Entry time: Tue Oct 11 03:35:16 2011     Reply to this: 5649   5656
Author: kiwamu 
Type: Update 
Category: LSC 
Subject: BS actuator reponse at low frequency : measured 

The response of the BS actuator in a low frequency regime has been measured.

After the measurement I did a coarse fit to see if the low frequency data agree with the high frequency response which I have measured two weeks ago (#5583)
So far it shows a good agreement with the high frequency data (see the plot below). Tomorrow I will do a serious fitting.
Once the calibration of BS is done, the low frequency responses of ITMs, PRM and SRM will be done by simply exciting BS and comparing them (maybe at a couple of frequency points around 0.1Hz).
BSactuator.png

(Measurement)

 + With free swinging MICH, the sensor (AS55_Q) was calibrated into counts/m.

     => The peak-peak counts was about 110 counts. So the sensor response is about 6.5x108 counts/m

 + Locked Michelson with AS55_Q and the signal was fedback to BS.

 + Set the UGF high enough so that the open loop gain below 10 Hz is greater than 1.

 + With DDT's swept sine measurement, C1:LSC-MICH_EXC was excited with a big amplitude of 40 counts.

 + Took a transfer function from C1:LSC-MICH_OUT to C1:LSC-MICH_EXC.

 + Calibrated the transfer function into m/counts by dividing it with the sensor response.

Quote from #5641
One possible reason is that my actuator responses are not so accurate below 1Hz.
I will measure the DC response of all the actuators and it will completely determine the shapes of the actuator responses except for the region around the resonance.

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