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Entry  Tue May 12 18:16:17 2020, gautam, Update, LSC, Relative importance of losses in the arm and PRC armLossVSPRCloss.pdf
    Reply  Tue May 12 20:16:31 2020, Koji, Update, LSC, Relative importance of losses in the arm and PRC 
       Reply  Tue May 12 22:47:49 2020, gautam, Update, LSC, Relative importance of losses in the arm and PRC 
Message ID: 15328     Entry time: Tue May 12 22:47:49 2020     In reply to: 15327
Author: gautam 
Type: Update 
Category: LSC 
Subject: Relative importance of losses in the arm and PRC 

Yes, \eta_A is the (average) round-trip loss for an arm cavity. I'd estimate this is ~100ppm currently. I edited the original elog to fill in this omission.

The RC mirror specs require some guesswork - the available specs for the Laseroptik mirrors (PR3) are for a 48 degree angle of incidence, and could be as high as 0.5 %. According to the poster, the spec is 2.6% loss inside the recycling cavity but I don't know where I got the number for the AR surface of the G&H PR2, and presumably that includes some guess I made for the MM between the PRC and the arm. Previously, assuming ~1-2% loss inside the RC gave good agreement between model and measurement. Certainly, if we assume similar numbers, a recycling gain of ~11 (200 * T_P=5.637%) is reasonable. But I think we need more data to make a stronger statement.

Quote:

Is \eta_A the roundtrip loss for an arm?

Thinking about the PRG=10 you saw:
- What's the current PR2/3 AR? 100ppm? 300ppm? The beam double-passes them. So (AR loss)x4 is added.
- Average arm loss is ~150ppm?

Does this explain PRG=10?

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