Sheila, Georgia, Craig

• Earlier today we lowered the gain of DHARD Y by 6dB, which makes it more stable.
•  Attached are measurements vs models of DHARD P+Y and CHARD Y.  DHARD P matches the model pretty well, and we have been able to engage the boost that we use for powering up.  
• DHARD Y has the gain we need to engage the boost, but engaging the boost isn't stable.  
• For yaw CHARD and DHARD match each other fairly well, and neither matches the model very well around the resonances around 1.5 Hz.  Based on the comparison to DHARD, we should be able to use 20 dB more gain for CHARD, but we find that we are not able to increase the gain without an instability.  
• We are also still limited to a very low gain for CHARD P. 
• We tried turning the optical levers back on, but this hasn't helped the stability of the CHARD loops.  
• We are now wondering if our problem is a cross coupling with the AS centering loops, or another ASC loop.  
• Since we are thinking that a cross coupling with another loop is our problem with CHARD, we attempted to increase their gains in the guardian state ENGAGE_REFL_POP_WFS, where the only ASC loops engaged are MICH, DHARD, CHARD, INP1, and PRC2 (POPX-> PR2).  Here we still see that they are unstable.  While we were sitting in this state, we saw a slowly growing instability at nearly 10 Hz which we were able to reduce by lowering the gains of the refl centering loops.  
• We took measurements of all 4 refl centering loops at DRMI, all 4 of these measurements can be found in /ligo/svncommon/IscSVN/iscmodeling/trunk/ALIGOH1/ASC_loops/Measurements/DC_centering/
• For DC2P we also took a measurement on resonance before engaging any of the REFL WFS, and we can see that the gain is reduced compared to DRMI by 1dB at high frequencies.   The second set of 4 attachments to this alog are comparisons of the REFL centering loops at DRMI and on resonance. 
• After measuring the REFL centering loop we had a look at the AS centering loops and found that they had barely any gain.  Comparing to Gabriele's log we saw that the gain was reduced by a factor of 5, which happened on August 23rd.  We set the gain back up by a factor of 5 for all 4 AS centering loops. 

We need to turn the gain of the CHARD loops up before we can power up, but haven't been able to so far.