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 Tue May 12 18:16:17 2020, gautam, Update, LSC, Relative importance of losses in the arm and PRC Tue May 12 20:16:31 2020, Koji, Update, LSC, Relative importance of losses in the arm and PRC Tue May 12 22:47:49 2020, gautam, Update, LSC, Relative importance of losses in the arm and PRC
Message ID: 15326     Entry time: Tue May 12 18:16:17 2020     Reply to this: 15327
 Author: gautam Type: Update Category: LSC Subject: Relative importance of losses in the arm and PRC

Attachment #1 is meant to show that having a T=500ppm PR2 optic will not be the dominant contributor to the achievable recycling gain. Nevertheless, I think we should change this optic to start with. Here, I assume:

• \eta_A denotes the (average) round trip loss per arm cavity (i.e. ITM + ETM). Currently, I guess this is ~100ppm.
• Fixed 0.5% loss from mode mismatch between the CARM mode and the PRC mode (the x-axis does NOT include this number).
• No substrates/AR coatings inside the cavity.
• For the nominal case, let's say the intracavity loss sums to 100 ppm.
• For the T=500ppm PR2, I assumed a total of 550 ppm loss in the PRC.

In relaity, I don't know how good the MM is between the PRC and the arms. All the scans of the arm cavity under ALS control and looking at the IR resonances suggest that the mode-matching into the arm is ~92%, which I think is pretty lousy. Kiwamu and co. claim 99.3% matching into the interferometer, but in all the locks, the REFL mode looks completely crazy, so idk

 Attachment 1: armLossVSPRCloss.pdf  109 kB  Uploaded Wed Jun 3 19:07:42 2020
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