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Message ID: 8842     Entry time: Sat Jul 13 03:27:20 2013
Author: Annalisa 
Type: Update 
Category: Green Locking 
Subject: Y arm caity scan 

I started doing a scan of the Y arm cavity with IR with ALS enabled.

ALS servo tuning:

The servo tuning procedure is basically the same as described in elog 8831.

This time I had a stronger beat note(-14 dBm instead of -24 dBm of the last measurement) thanks to a better alignment.

Plot1 shows the Power spectrum of the BEATY_PHASE_OUT. The RMS is smaller by a factor of 2 (400Hz), corresponding to a residual motion of about 25 pm.

Offset setting avity scan

In order to give an offset linearly growing in time, I used the ezcastep script instead of giving the offset in OFFSETTER2. If the ramp time is long enough, it is not necessary to enable the 30mHz filter.

To span 2 FSR, I started from an offset of 450 and I gave a maximum value of 1600 with a delay of 0.2s between two consecutive steps.

Cavity scan

I did a first scan with the cavity well aligned, basically to know the position of the 00 peaks and choose the best offset range (Plot2)

Then I misaligned the TT2, first in PITCH and yhen in YAW, in order to enhance the HOMs. (Plot3 and Plot4)

More investigation and measurements needed. 



Attachment 1: PowerSpectrum0712  22 kB
Attachment 2: ScanCavityAligned.pdf  67 kB  Uploaded Sat Jul 13 04:28:08 2013  | Hide | Hide all
Attachment 3: ScanCavityMisPitch.pdf  75 kB  Uploaded Sat Jul 13 04:31:46 2013  | Hide | Hide all
Attachment 4: ScanCavityMisYaw.pdf  81 kB  Uploaded Sat Jul 13 04:41:35 2013  | Hide | Hide all
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