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Entry  Tue Jun 4 00:17:15 2019, gautam, Update, BHD, Preliminary BHD calculations LOreqs.pdf
    Reply  Thu Jun 6 18:49:22 2019, gautam, Update, BHD, Preliminary BHD calculations darkPortScatter.pdfOMCbackscatter.pdfdirectScatter.pdf
       Reply  Wed Jul 3 11:47:36 2019, gautam, Update, BHD, PRC filtering PRCfiltering.pdf
          Reply  Wed Jul 31 09:41:12 2019, gautam, Update, BHD, OMC cavity geometry paramSpaceHeatMap.pdf
             Reply  Wed Jul 31 17:57:35 2019, Koji, Update, BHD, OMC cavity geometry 
             Reply  Fri Aug 23 10:01:14 2019, gautam, Update, BHD, OMC cavity geometry - some more modeling modeContentComparison.pdfOMCtransComparison.pdf
       Reply  Tue Aug 6 15:52:06 2019, gautam, Update, BHD, Preliminary BHD calculations OMCbackscatter.pdf
Message ID: 14722     Entry time: Wed Jul 3 11:47:36 2019     In reply to: 14658     Reply to this: 14819
Author: gautam 
Type: Update 
Category: BHD 
Subject: PRC filtering 

A question was raised as to how much passive filtering we benefit from if we pick off the local oscillator beam for BHD from the PRC. I did some simplified modeling of this. For the expected range of arm cavity round trip losses (20-50 ppm), I think that the 40m CARM pole will be between 75-85 Hz. The corresponding recycling gain will be 40-50, with the current PRM. I assumed 1000 ppm loss inside the PRC. The net result is that, assuming the single pole coupled cavity response, we will get ~8-9 dB of filtering at ~200 Hz of the intensity noise of the input laser field to the interferometer if we pick the LO beam off from the PRC (e.g. PR2 transmission), instead of picking it off before.

The next questions are: (i) can we do a sufficiently good job of achieving the required RIN stability on the LO field for BHD without relying on the passive filtering action of the PRC? and (ii) is the benefit of the PRC filtering ruined in the process of routing the LO field from wherever the pickoff happens to the BHD setup?

Attachment 1: PRCfiltering.pdf  18 kB  Uploaded Wed Jul 3 12:51:48 2019  | Show | Show all
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