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Entry  Thu Sep 29 20:21:29 2016, Johannes, Update, General, YARM loss measurement 
    Reply  Mon Oct 3 21:24:02 2016, Johannes, Update, General, XARM loss measurement ReflectionLoss.pdf
       Reply  Tue Oct 4 22:18:24 2016, Johannes, Update, General, X/YARM loss measurement anomalousData.png
          Reply  Wed Oct 5 19:10:04 2016, gautam, Update, General, Arm loss measurement review 
             Reply  Mon Nov 14 19:15:57 2016, Johannes, Update, General, Achievable armloss measurement accuracy 
                Reply  Tue Nov 15 20:35:19 2016, Johannes, Update, General, Achievable armloss measurement accuracy 
                   Reply  Thu Nov 17 21:54:11 2016, Johannes, Update, General, Achievable armloss measurement accuracy 
                      Reply  Thu Jan 12 02:45:53 2017, Johannes, Update, General, Next armloss steps ass_illustration.pdf
                         Reply  Fri Jan 13 08:54:32 2017, Johannes, Update, General, DC PD installed ASDCPD_up.jpgASDCPD_down.jpgscrambled_osci.jpg
Message ID: 12524     Entry time: Thu Sep 29 20:21:29 2016     Reply to this: 12528
Author: Johannes 
Type: Update 
Category: General 
Subject: YARM loss measurement 

[Gautam, Johannes]

I scripted a series of YARM DC reflectivity measurements last night alternating between locked state and unlocked state (with ETMY misaligned) for measuring the after-vent armloss. The general procedure is based on elog 11810, but I'll also give a brief summary here.

  • To measure the locked reflectivity the dither script is executed with a stop condition that depends on the rms values of its error signals.
  • The dithering is stopped, and while the arm is locked the reflected power is recorded from both POX/POY DC and ASDC, as well as the mode cleaner transmission for normalization.
  • The arm locking is switched off, and ETMY moved to is 'misaligned' position. This gets rid off unwanted mode flashes.
  • In the unlocked state the same quantities are recorded.
  • Rinse and repeat for a set number of times (for this run I set it to 100 and left the interferometer alone).

I did this back in June (but strangely never posted what I found, shame on me). What I found back then was a YARM loss of 237 ppm +/- 41 ppm and an XARM loss of 501 ppm +/- 105 ppm

Last night's data indicates a YARM loss of 143 ppm +/- 24 ppm after cleaning with first contact. yeslaugh

THIS IS STILL ASSUMING THAT THE MODE-MATCHING HASN'T CHANGED. We had however moved ETMY closer to ITMY during the vent by 19mm. Gautam and I had some trouble setting up the ALS to confirm the mode-matching, but we're in the process of recovering the XARM IR beat.

ELOG V3.1.3-