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Entry  Fri Apr 24 01:16:30 2015, Jenne, Update, ASC, Broken Xass? 
    Reply  Sat Apr 25 03:32:45 2015, Koji, Update, ASC, Broken Xass? 
       Reply  Sun Apr 26 01:10:18 2015, rana, Update, ASC, unBroken Xass? xasstune_150426.pngxassnoise.pdf
          Reply  Sun Apr 26 15:05:35 2015, Jenne, Update, ASC, unBroken Xass? 
Message ID: 11253     Entry time: Sun Apr 26 01:10:18 2015     In reply to: 11248     Reply to this: 11255
Author: rana 
Type: Update 
Category: ASC 
Subject: unBroken Xass? 

Today I tried some things, but basically, lowering the input gain by 10 made the thing stable. In the attached screenshotstrip, you can see what happens with the gain at 1. After a few cycles of oscillation, I turned the gain back to 0.1.

There still is an uncontrolled DoF, but I that's just the way it is since we only have one mirror (the BS) to steer into the x arm once the yarm pointing is fixed.

Along the way, I also changed the phase for POX, just in case that was an issue. I changed it from +86 to +101 deg. The attached spectra shows how that lowered the POX_Q noise.

I also changed the frequencies for ETM_P/Y dither from ~14/18 Hz to 11.31/14.13 Hz. This seemed to make no difference, but since the TR and PO signals were quieter there I left it like that.

This is probably OK for now and we can tune up the matrix by measuring some sensing matrix stuff again later.

Attachment 1: xasstune_150426.png  97 kB  | Show | Hide all | Show all
Attachment 2: xassnoise.pdf  22 kB  | Hide | Hide all | Show all
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