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Entry  Mon Jul 11 11:56:40 2022, he Yehonathan, Update, BHD, MICH AS55 noise budget Control_Diagram.pdfMICH_AS55_Noise_Budget.pdf
    Reply  Tue Jul 12 09:14:50 2022, rana, Update, BHD, MICH AS55 noise budget 
       Reply  Wed Jul 13 10:54:39 2022, Yehonathan, Update, BHD, MICH AS55 noise budget BS_MICH_ACtuation_Calibration.pdfMICH_AS55_Model_Measurement_Comparison.pdfMICH_AS55_Noise_Budget.pdf
          Reply  Wed Jul 13 13:30:48 2022, Yehonathan, Update, BHD, add Laser RIN to MICH budget 
             Reply  Mon Jul 18 16:49:57 2022, Yehonathan, Update, BHD, add Laser RIN to MICH budget Laser_RIN.pdfMICH_AS55_Noise_Budget.pdf
                Reply  Mon Jul 18 18:33:38 2022, Koji, Update, BHD, add Laser RIN to MICH budget 
Message ID: 17013     Entry time: Mon Jul 18 16:49:57 2022     In reply to: 16999     Reply to this: 17015
Author: Yehonathan 
Type: Update 
Category: BHD 
Subject: add Laser RIN to MICH budget 

I measured the RIN by taking the spectrum of C1:MC_TRANS_SUMFILT_OUT and dividing it by the mean count on that channel (~13800 cts). Attachment 1 shows the result.

I updated the MICH AS55 noise budget but got a very low contribution (gold trace in attachment 2).

It seems too low I think. What could've gone wrong? Finesse calculates that the transfer function from laser amplitude modulation to AS55 is ~ 1.5e-9 at DC. If I turn off HOMs I get 1e-11 at DC, so this coupling is a result of some contrast defect. Should I include some RMS imbalances in the optics to account for this? Should I include it as a second-order effect due to MICH RMS deviation from zero crossing?

Quote:

the main laser noise coupling for a Michelson is because of the RIN, not the frequency noise. You can measure the RIN, in MC trans or at the AS port by getting a single bounce beam from a single ITM.

 

Attachment 1: Laser_RIN.pdf  19 kB  Uploaded Mon Jul 18 17:57:30 2022  | Hide | Hide all
Laser_RIN.pdf
Attachment 2: MICH_AS55_Noise_Budget.pdf  80 kB  Uploaded Mon Jul 18 18:00:24 2022  | Hide | Hide all
MICH_AS55_Noise_Budget.pdf
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