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Entry  Mon Nov 7 17:38:18 2011, Katrin, Update, Green Locking, YARM length fluctuation fluctuation.pngfluctuation_length.pngfluctuation_Hz_length.png
    Reply  Mon Nov 7 22:20:18 2011, kiwamu, Update, Green Locking, Re:YARM length fluctuation 
Message ID: 5837     Entry time: Mon Nov 7 17:38:18 2011     Reply to this: 5838
Author: Katrin 
Type: Update 
Category: Green Locking 
Subject: YARM length fluctuation 

fluctuation.png

I measured the power spectrum of channel C1:GCY_SLOW_SERVO1_IN1, which is the PZT driving voltage.

I converted the output to a PSD. Next, I converted counts/sqrt(Hz) to volts/sqrt(Hz) by multiplying with 40 V / 2^16 counts.

Finally, I multiplied it with 5MHz/V for the PZT to end up with Hz/sqrt(Hz).

 

This corresponds to a cavity length fluctuation of

fluctuation_length.png

with lambda = 532nm and a YARM cavity length of 37.757m (elog # 5626).

All in one plot

fluctuation_Hz_length.png

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