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Message ID: 1432     Entry time: Thu Mar 26 04:09:38 2009
Author: Yoichi 
Type: Update 
Category: IOO 
Subject: Single X arm lock spectra with different MC lock schemes 
The attached plots show MC_F, FSS_FAST_F and XARM IN/OUT spectra with different MC locking modes.
The conventional locking means the FSS is used. The direct frequency lock is the new way.
You can see that at low frequencies, the frequency actuator is working hard to suppress the MC pendulum motions.
The X-arm also sees a lot of frequency noise at low frequencies because of this.
The transmitted power of the X-arm fluctuates a lot making it difficult to align the mirrors.

The zoomed plots show that the structures in the kHz band are also present in the case of the direct frequency lock, although the frequencies are somewhat different.
Attachment 1: XarmSpectra.pdf  111 kB  | Hide | Hide all | Show all
XarmSpectra.pdf
Attachment 2: XarmSpectraZoom.pdf  171 kB  | Show | Hide all | Show all
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