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Entry  Fri Nov 18 15:45:11 2011, Mirko, Update, IOO, Mode cleaner noise projection WholeMCNoiseProjection.pngWholeMCNoiseProjection.fig
    Reply  Fri Nov 18 19:57:19 2011, Mirko, Update, IOO, Mode cleaner noise projection MC_ELP.pngWithAndWithoutHPs.pdfSeismCoh.pdf
       Reply  Fri Nov 18 23:44:33 2011, rana, Update, IOO, Mode cleaner noise projection 
          Reply  Sat Nov 19 01:26:16 2011, Den, Update, IOO, Mode cleaner noise projection 
          Reply  Sat Nov 19 12:57:55 2011, Mirko, Update, IOO, Mode cleaner noise projection CouplingMClengthsToMCF.pdfNpModeCleaner.pdf
Message ID: 5957     Entry time: Sat Nov 19 01:26:16 2011     In reply to: 5953
Author: Den 
Type: Update 
Category: IOO 
Subject: Mode cleaner noise projection 

Quote:

Instead, what we want is to project how the actual OSEM noise in the presence of no signal shows up as MC length. For that we should use the old traces of the OSEM noise with no magnets and then inject that spectrum of noise into the SUSPOS filter bank with all the loops running. We can then use this TF to estimate the projection of OSEM noise into the MC length.

That's right. The easier problem arises if we consider one of  MC mirrors. The coherence between OSEM sensors and GUR1_X in free moving regime is equal to 0.9 at frequencies 0.1 - 1 Hz. But with local dumping coherence is 0.6. We have

Mirror -> Sensor -> Satellite Module -> Whitening -> ADC -> Computer -> DAC -> Dewhitening -> Satellite Module -> Actuator -> Mirror

Somewhere we produce noise that kills part of coherence. We can use this method with the injection of spectrum of noise into the SUSPOS filter bank only for one mirror and see how the coherence between OSEM sensor and GUR1_X will change. If the change is small, we deal with something else. It the coherence will change from 0.6 to ~0.4, than we have big OSEM noise.

It might be also the problem that the amplitude of COIL_OUT signal is ~25. If it is in counts we may have noise from DAC. 

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