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Message ID: 5619     Entry time: Tue Oct 4 20:34:20 2011
Author: Katrin 
Type: Update 
Category: Green Locking 
Subject: 7kHz Peak in servo input YARM 

[Kiwamu, Katrin]

As reported earlier an oscillation around 7kHz is an the PDH error signal. The lower spectrum show that there is a peak from 6-7kHz.

This peak is somehow dependent on the modulation frequency. This means the peak can be shifted to a higher frequency when the modulation frequency is increased (see for comparsion f_mod=279kHz).

If the power supply for the green PD is switched of the peak vanishes. The same happens if the LO is switched of.

servoinput.png servoinput2.png

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