40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
 40m Log Not logged in Message ID: 3699     Entry time: Tue Oct 12 17:42:57 2010
 Author: yuta Type: Update Category: SUS Subject: very first measurement of Q-values for MC1

Background:
Data aquisition system is fixed, and now we can use the Dataviewer to measure Q-values of the ringdowns for each DOF, each optics.
First of all, I measured MC1 suspention damping servo for a test.

What I did:
1. Used DAQ channels activated in this entry(#3690) to see and compare the ringdowns when the damping servo is on and off with the Dataviewer.

2. Plotted the data and fitted the ringdown using this formula;
p*exp(-p*t)*sin(p*t+p)+p
I used python's scipy.optimize.leastsq for the fitting.

3. Calculated the resonant frequency f0 and Q-value using following formulas;
f0=2*pi*sqrt(p**2+p**2)
Q=f0/(2*pi)/(2*p)

4. For plotting, I subtracted the offset(=p).

All parameters I used for this measurement are automatically saved here;
/cvs/cds/caltech/burt/autoburt/snapshots/2010/Oct/12/13:07/c1mcs.epics
(-1,0,1 for all matrix elements, GAIN=3,3,3,150 for POS,PIT,YAW,SIDE)

Result:
Attached is the plot of each 4 DOF ringdown when servo is off and on.
"servo off" means off for that DOF. Servo for the other 3 DOFs are on.

As you can see clearly, the damping servo is working.

The resonant frequencies and Q-values calculated from the fitting are as follows;

 servo off servo on f0 (Hz) Q f0 (Hz) Q POS 0.97 large 0.97 16 PIT 0.71 96 0.73 6.9 YAW 0.80 100 0.82 8.9 SIDE 0.99 large 0.99 27

Resonant frequencies and Q-values have about 1% and 10% error respectively.
I estimated it from my 2-time measurement of the POS ringdown.

Next work:
- Find and modify some scripts to optimize the matrix elements
- Calibrate the displacement
- Do the same thing for other optics

 Attachment 1: MC1ringdown.png  473 kB ELOG V3.1.3-