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Entry  Mon Aug 17 23:36:10 2020, gautam, Update, ALS, Whitening and ALS noise ALSimprovement.pdf
    Reply  Tue Aug 18 13:55:23 2020, rana, Update, ALS, Whitening and ALS noise 
Message ID: 15531     Entry time: Mon Aug 17 23:36:10 2020     Reply to this: 15533
Author: gautam 
Type: Update 
Category: ALS 
Subject: Whitening and ALS noise 

finally managed to install a differential-receiving whitening board in 1Y2 - 4 channels are available at the moment. As I claimed, one stage of 15:150 Hz z:p whitening does improve the ALS noise a little, see Attachment #1. While the RMS (from 1kHz-0.5 Hz) does go down by ~10 Hz, this isn't really going to make any dramatic improvement to the 40m lock acquisiton. Now we're really sitting on the unsuppressed EX laser noise above ~30 Hz. This measurement was taken with the arm cavities locked with POX/POY, and end lasers locked to the arm cavities with uPDH boxes as usual. This was just a test to confirm my suspicion, the whitening board is to be used for the air BHD channels, but when we get a few more stuffed, we can install it for the ALS channels too.

Attachment 1: ALSimprovement.pdf  157 kB  Uploaded Tue Aug 18 00:36:35 2020  | Hide | Hide all
ALSimprovement.pdf
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