Ryan C, Sheila D

Summary:  The input beam moved after the PSL incursion, alinging the IMC doesn't completely restore the input beam alignment to the IFO.  Using IM4 QPD as a reference to move IM3 resulted in no beam on the ISS second loop, so we have reverted that for now.

Before Tuesday's PSL incursion, when the IMC was locked at 2W IM4 trans QPD was fairly well centered, we had 1.5 or 1.6 counts on the ISS second loop inner and outer loop sums, 310 counts on MC2 trans QPD, and 95 counts on the ISS second loop QPD.  After Jenne relocked the IMC yesterday, we had 2W on IM4 trans, but the QPD was off center with ~0.3 pit and 1 in yaw, the second loop inner and outer sums were 1.46 and 1.6, 305 counts on MC2 trans, and 94 on ISS second loop QPD. 

This morning Camilla and company moved IM3 to re-center the beam on IM4 trans, 78831,  After our struggles with input alignment after the vent earlier this year, we learned that LLO uses IM4 QPD as a reference to adjust IM3 trans when needed, so we had centered IM4 hoping to use it as a reference in this way.  However, doing this made the beam completely fall off the ISS second loop, with no power on it's QPD or the two PD sum channels.  This may mean that we were close to clipping in the second loop before, so we should come back to this another day to think about how we can restore the input alignment to what it previously was, and make sure we don't clip on the ISS. 

For now I reverted IM3 sliders to this morning, and Ryan is working his way through the initial alignment. 

Along the way he also showed me that the X arm green transmission is extremely noisy, with high frequency fuzz.  This might mean that we still have some electronics problems at EX after today's work.  Sicne Ryan has been able to get past ALS locking tonight, we won't try to address this issue tonight.