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Entry  Wed Oct 5 22:59:11 2011, Koji, Frank, Notes, Seismic, mechanical properties of new stack  
    Reply  Thu Oct 6 03:37:44 2011, Koji, Notes, Seismic, Modeling of the vertical isolation of the stack vertical_isolation.pdfvertical_isolation.zipvertical_isolation_plot.pdf
       Reply  Tue Oct 25 22:03:32 2011, frank, tara, Notes, Seismic, Modeling of the vertical isolation of the stack nb.png
          Reply  Wed Oct 26 18:05:49 2011, frank, tara, Notes, Seismic, Modeling of the vertical isolation of the stack 6x
             Reply  Thu Oct 27 20:45:58 2011, frank, tara, Notes, Seismic, ring down measurement for rubber spring fit4.pngfit1.pngcomparefit.pnghist.png
                Reply  Thu Nov 3 01:55:03 2011, Frank, Notes, Seismic, ring down measurement for rubber spring 
             Reply  Fri Oct 28 14:04:22 2011, frank, tara, Notes, NoiseBudget, Noise budget for unfloated table beat_27.pngbeat_27.fig
                Reply  Wed Nov 16 19:11:38 2011, tara, Notes, NoiseBudget, seimic coupling to beat noise 
                   Reply  Thu Nov 17 23:30:19 2011, tara, Notes, NoiseBudget, vertical seismic coupling to beat noise SETUP_2011_11_17.pngfreq_resp.pngfreq_resp.fig
                      Reply  Wed Nov 30 19:00:42 2011, tara, Notes, NoiseBudget, vertical seismic coupling to beat noise Seismic_resp.pngSeismic_resp.figSNR.png
Message ID: 741     Entry time: Wed Nov 30 19:00:42 2011     In reply to: 735
Author: tara 
Type: Notes 
Category: NoiseBudget 
Subject: vertical seismic coupling to beat noise 

  From 40m page, COMSOL FEA gives us the coupling (from vertical seismic to frequency noise ) to be 53 [kHz / (m/s2)].

Seismic_resp.png

Fig1: TF measurement( from PSL:735). This time the estimation from FEA is plotted as well.

    ==comments==

  •      From ACAV/seismic (Green), the measurement is ~ 1order of magnitude higher than the FEA result. This might come from the fact that the support is not exactly at the right place
  •      From RCAV/seismic (red), the TF tells us nothing. The coherence is close to zero, and the SNR is very low (~10-6 - 10-5). This requires 1010 average to bring SNR to 1. Below is the plot for Signal (frequency noise due to seismic) and noise (NPRO free running noise. And SNR (Signal/Noise)

SNR.png

     fig 2: Signal and Noise in TF measurement between RCAV noise and seismic.

        The NPRO free running noise is from psl:617. Seismic noise is measured by an accelerometer (PSL:716)and converted to frequency noise using coupling from FEA result (53kHz / (m/s^2))

  ==what's next==

  1.  Since the SNR for RCAV noise/seismic is very small, we might have to shake the table and remeasure it.
  2.  Use a better seismometer. The current accelerometer might not be sensitive enough.
  3. Check the coupling from FEA, check what is the coupling as a function of supporting position.
Attachment 2: Seismic_resp.fig  91 kB
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