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Entry  Sat May 9 17:01:08 2020, Yehonathan, Update, Loss Measurement, 40m Phase maps loss estimation ITMX_Loss_Map.pdfETMX_Loss_Map.pdfITMX_Phase_Map_(nm).pdfETMX_Phase_Map_(nm).pdf
    Reply  Wed May 13 15:13:11 2020, Yehonathan, Update, Loss Measurement, 40m Phase maps loss estimation ITMX_Loss_Map.pdfETMX_Loss_Map.pdf
       Reply  Thu May 14 12:21:56 2020, Yehonathan, Update, Loss Measurement, 40m Phase maps loss estimation ITMX_Loss_Map_Perturbation_Theory.pdfETMX_Loss_Map_Perturbation_Theory(1).pdf
          Reply  Thu May 14 19:00:43 2020, Yehonathan, Update, Loss Measurement, 40m Phase maps loss estimation 
             Reply  Tue May 19 15:39:04 2020, Yehonathan, Update, Loss Measurement, 40m Phase maps loss estimation Mode_power_fraction1.pdf
Message ID: 15323     Entry time: Sat May 9 17:01:08 2020     Reply to this: 15329
Author: Yehonathan 
Type: Update 
Category: Loss Measurement 
Subject: 40m Phase maps loss estimation 
I took the phase maps of the 40m X arm mirrors and calculated what is the loss of a gaussian beam due to a single bounce. I did it by simply calculating 1 - (overlap integral)^2 where the overlap is between an input Gaussian mode (calculated from the parameters of the cavity. Waist ~ 3.1mm) and the reflected beam (Gaussian imprinted with the phase map). The phase maps were prepared using PyKat surfacemap class to remove a flat surface, spherical surface, centering, etc. (Attachments 3, 4)
 
I calculated the loss map (Attachments 1,2: ~ 4X4 mm for ITM, 3X3mm for ETM) by shifting the beam around the phase map. It can be seen that there is a great variation in the loss: some areas are < 10 ppm some are > 80 ppm.
 
For the ITM (where the beam waist is) the average loss is ~ 23ppm and for the ETM its ~ 61ppm due to the enlarged beam. The ETM case is less physical because it takes a pure gaussian as an input where in reality the beam first interacts with the ITM.
 
I plan to do some first-order perturbation theory to include the cavity effects. I expect that the losses will be slightly lower due to HOMs not being completely lost, but who knows.
 
Attachment 1: ITMX_Loss_Map.pdf  18 kB  Uploaded Sat May 9 18:04:22 2020  | Hide | Hide all
ITMX_Loss_Map.pdf
Attachment 2: ETMX_Loss_Map.pdf  19 kB  Uploaded Sat May 9 18:04:30 2020  | Hide | Hide all
ETMX_Loss_Map.pdf
Attachment 3: ITMX_Phase_Map_(nm).pdf  53 kB  Uploaded Sat May 9 18:11:05 2020  | Hide | Hide all
ITMX_Phase_Map_(nm).pdf
Attachment 4: ETMX_Phase_Map_(nm).pdf  79 kB  Uploaded Sat May 9 18:11:15 2020  | Hide | Hide all
ETMX_Phase_Map_(nm).pdf
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