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Message ID: 93     Entry time: Sat Aug 20 22:18:26 2016
Author: Gabriele 
Type: General 
Category: Daily Progress 
Subject: First measured Qs 

Using the first ring down of the day (GPS 1155754513 + 3600 seconds), I computed the amplitude of each of the modes already identified, using a short FFT spectrogram (each FFT is 1 second long, overlap of 0.5 s).

Then I used the same code I developed at LMA to fit the ring down, including the beat between the unresolved mode pairs. The fit is versy sensitive to the initial conditions, so I had to fine tune them for each of the 20 modes. Still, all fits were successful with 30 minutes of work.

Here are all the fits:

And in summary all the measured Qs, which turned out to be larger than what I was expecting, considering that the disk is not annealed.

The analysis code in MATLAB is attached.

Attachment 22: first_ringdown.m  27 kB  Uploaded Sat Aug 20 23:24:57 2016  | Hide | Hide all
%% Compare data right before and right after the excitation
gps0 = 1155754000;
gps1 = 1155754513;
dt = 180;

c = nds2.connection('cymac3.ligo.caltech.edu', 8088);
data0 = c.fetch(gps0, gps0+dt, {'X3:CR1-X_NORM_OUT_DQ', 'X3:CR1-Y_NORM_OUT_DQ', 'X3:CR1-ESD_OUT_DQ'});
data1 = c.fetch(gps1, gps1+dt, {'X3:CR1-X_NORM_OUT_DQ', 'X3:CR1-Y_NORM_OUT_DQ', 'X3:CR1-ESD_OUT_DQ'});

x0 = data0(1).getData();
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