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Entry  Mon Feb 28 10:58:13 2011, Frank, Notes, NoiseBudget, Seismometer installed 
    Reply  Tue Mar 1 08:43:06 2011, rana, Notes, NoiseBudget, Seismometer installed 
       Reply  Tue Mar 1 11:32:35 2011, Frank, Notes, NoiseBudget, Seismometer installed 
Message ID: 523     Entry time: Tue Mar 1 11:32:35 2011     In reply to: 522
Author: Frank 
Type: Notes 
Category: NoiseBudget 
Subject: Seismometer installed 

right! my hope was as the pendulum frequencies of the cavity also shows up in the seismometer we can use that  to feed back to my little piezo shaker and reduce the effect a little bit.
The TF measurement is NOT for the fringe wrapping, it's for all the other stuff we see in the spectrum.
My hope was that we can gain at least little information about that for better noise estimate which does not couple through the cavity. So far our model only takes the cavity into account, not the rest.


The fringe wrapping signal comes from the velocity difference between the table and the cavity. You can calculate the spectrum of this by propagating the seismometer spectrum through the single pendulum approximation for the cavity.

For the feedback, you only have to suppress the seismometer signal. Since the fringe wrapping is nonlinear, its not predicted by the transfer function method.


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