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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: 15533     Entry time: Tue Aug 18 13:55:23 2020     In reply to: 15531
Author: rana 
Type: Update 
Category: ALS 
Subject: Whitening and ALS noise 

No, there should be no unscheduled visits from any inspector, marshal, tech, or vendor. They all have to be escorted or they don't get in. If they have a problem with that, please give them my cell #.


For the ALS, in addition to the beat note spectrum, I think we need to know the loop gain use to feedback to the ETM to determine the true cavity length fluctuation. w/o ALS, the noise would be only due to the seismic noise, OSEM damping noise, and the IR-PDH residual. Those are all suppressed by the ALS loop, but then the ALS loop puts its sensing noise onto the cavity. So, if I'm thinking about this right, the ALS beat noise > 200 Hz doesn't matter so much to the CARM RMS. So the whitening seems to be doing good in the right spot, but we would like to have another boost in the green PDH to up the gain below ~300 Hz?

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