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Message ID: 5928     Entry time: Thu Nov 17 17:03:28 2011
Author: MIrko 
Type: Update 
Category: IOO 
Subject: MC noise projection 

Another go at the noise projection from MC1-3 pit/yaw to MC length. This time injecting into the MC autoalignment FB (e.g. C1:IOO-WFS1_PIT_EXC ).

LTPDA is working now, but still the NDS server is not so cooperative.

Summary: Alignment fluctuations of the MC mirrors don't significantly contribute to MC length changes up to at least 3.5Hz. Especially they can't explain the lack of coherence between seismometers and MC length below 1Hz that we worry about for the OAF.

At high frequencies >= 10Hz you can see angle to length coupling as is evident in Sureshes spot position measurements.

Whiteish noise injection:

Injection from 0.1-20Hz.Filtered by the servo filters and zp:[1],[1] , Gain = 1 @ 2Hz

 MCLengthToAngleCouplingNoiseProjection.png

Look at the coherence plots for the quality of the measurement:

Coherence_WFS1pit.png

Coherence_WFS2pit.png

 

Coherence_WFS1yaw.png

 Coherence_WFS2yaw.png

Injection details:

DOF      Amplitude[counts]        UTC Time (duration always 4mins)
WFS1p  70                               22:28
WFS1y  55                               22:03
WFS2p  70                               22:13
WFS2y  70                               22:18
None      -                                 22:23

Fixed sine injections:

To get some better SNR at low frequencies I did a fixed sine noise injection at 0.3Hz. See attached files.

DOF      Amplitude[counts]        UTC Time (duration always 4mins)    Lower limit of SNR MC length via mirror misalignment
WFS1p  4                                  00:05                                                29.3
WFS1y  4                                  00:14                                                22.0
WFS2p  4                                  00:19                                                18.5
WFS2y  4                                  00:25                                                18.0

Attachment 2: WFS1pit.png  23 kB  Uploaded Thu Nov 17 18:22:22 2011  | Hide | Hide all
WFS1pit.png
Attachment 3: WFS1yaw.png  39 kB  Uploaded Thu Nov 17 18:22:37 2011  | Hide | Hide all
WFS1yaw.png
Attachment 4: WFS2pit.png  23 kB  Uploaded Thu Nov 17 18:22:49 2011  | Hide | Hide all
WFS2pit.png
Attachment 5: WFS2yaw.png  23 kB  Uploaded Thu Nov 17 18:23:01 2011  | Hide | Hide all
WFS2yaw.png
Attachment 7: Coherence_WFS2pit.png  26 kB  Uploaded Thu Nov 17 22:02:54 2011  | Hide | Hide all
Coherence_WFS2pit.png
Attachment 11: NpWfs.pdf  49 kB  Uploaded Thu Nov 17 22:14:09 2011  | Hide | Hide all
NpWfs.pdf NpWfs.pdf NpWfs.pdf NpWfs.pdf NpWfs.pdf
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