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Entry  Wed Jun 6 21:11:45 2012, yuta, Update, Green Locking, improved Y arm green alignment beatygreenpower20120606.png
    Reply  Thu Jun 7 02:25:27 2012, yuta, Update, Green Locking, improved Y arm green alignment - even more beatygreenpower20120607.png
       Reply  Thu Jun 7 07:27:27 2012, Koji, Update, Green Locking, improved Y arm green alignment - even more freq_noise_AUX.pdf
Message ID: 6780     Entry time: Thu Jun 7 07:27:27 2012     In reply to: 6776
Author: Koji 
Type: Update 
Category: Green Locking 
Subject: improved Y arm green alignment - even more 

Yes. The end PDH servo should be checked more carefully.

The end PDH seems to have insufficient gain at around 100Hz.
The attached is the ALS noise budget calculated with the simulink model for the green locking paper.

The residual error of the end AUX laser (green) is contributing to the final ALS signal (black).
In particular, the residual AUX frequency noise, which is shown as the blue, is contributing to the noise above 100Hz.

In the model I also confirmed that the servo still has a room for improvement.

By having more suppression of the AUX frequency noise, we will be able to increase the ALS servo bandwidth
without increasing the ALS residual RMS by a servo bump. This will give us the improvement of the seismic
noise suppression at 10Hz (i.e. more suppression of red).

Attachment 1: freq_noise_AUX.pdf  510 kB  Uploaded Thu Jun 7 08:28:20 2012  | Show | Show all
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