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Message ID: 1383     Entry time: Wed Mar 11 01:16:40 2009
Author: rana 
Type: Summary 
Category: IOO 
Subject: rogue trianglewave in the MC Servo offset slider 

On Monday evening, I ran this command: trianglewave C1:IOO-MC_REFL_OFFSET 0 4 120 600;ezcawrite C1:IOO-MC_REFL_OFFSET 1.76

which I thought (from the syntax help) would move that offset slider with a period of 120 seconds for 600 seconds. In actuality, the last argument is the

run time in number of periods. So the offset slider has been changing by 8 Vpp for most of the last day. Oops. The attached image shows what effect

this had in the MC transmitted power (not negligible). This would also make the locking pretty difficult.

 

In the second plot you can see the zoom in view for ~30 minutes. During the first part, the MCWFS are on and there are large fluctuations

in the transmitted power as the WFS offset changes. This implies that the large TEM00 carrier offset we induce with the slider couples into

the WFS signals because of imbalances in the quadrant gains - we need someone to balance the RF gains in the WFS quadrants by injecting

an AM laser signal and adjusting the digital gains.

 

Since there is still a modulation of the MC RFPD DC with the WFS on, we can use this to optimize the REFL OFFSET slider. The third plot

shows a 8 minute second trend of this. Looks like the slider offset of zero would be pretty good.

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Attachment 2: Untitled.png  24 kB  Uploaded Wed Mar 11 02:21:02 2009  | Show | Hide all | Show all
Attachment 3: a.png  21 kB  Uploaded Wed Mar 11 03:07:00 2009  | Show | Hide all | Show all
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