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Entry  Tue Jun 25 00:28:52 2013, rana, manasa, Update, LSC, Arm Cavity scan with X-ALS after ALS servo upgrade 6x
    Reply  Tue Jun 25 10:18:34 2013, Mystery Man, Update, LSC, Arm Cavity scan with X-ALS after ALS servo upgrade 
       Reply  Tue Jun 25 11:39:13 2013, Koji, Update, LSC, Arm Cavity scan with X-ALS after ALS servo upgrade 
    Reply  Thu Jun 27 19:17:03 2013, manasa, Update, LSC, Xarm ALS out-of-loop noise ALS_OoL.pdfALS_OoL1.pdf
Message ID: 8772     Entry time: Thu Jun 27 19:17:03 2013     In reply to: 8741
Author: manasa 
Type: Update 
Category: LSC 
Subject: Xarm ALS out-of-loop noise 

Measured frequency noise is ~10Hz/rtHz @100Hz. 

Measure the out-of-loop noise of Xarm ALS:

1. The X-arm was locked for IR using PDH error signal.

2. 'CLEAR HISTORY' of the phase tracker filters.

3. Measured the power spectrum of the phase tracker output. I have used the newly created calibrated channel "PHASE_OUT_DQ. So the phase tracker output now reads in Hz.

Discussion:

The measurement was done with beat note frequency at ~40MHz. The flat noise level of 10Hz/rtHz from 20-100Hz (in plot 2) is not good. We should investigate as to what sets this noise level. The spike at 60Hz is because the 60Hz frequency comb filter was not enabled.

I plan to the following to get a clearer outlook
1. Connecting the beat box to an RF source and measure the noise levels for a range of frequency inputs to the beatbox.
2. Measure the noise at C1:ALS-BEATX_FINE_I_IN1 (before the antiwhitening filters) and check whether the new whitening filters has done anything good with respect to minimizing the DAQ noise.

 

Attachment 1: ALS_OoL.pdf  13 kB  Uploaded Thu Jun 27 23:25:10 2013  | Hide | Hide all
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Attachment 2: ALS_OoL1.pdf  7 kB  Uploaded Thu Jun 27 23:37:28 2013  | Hide | Hide all
ALS_OoL1.pdf
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