[Jenne, Hang, Gabriele]

We had DRMI locked for long periods earlier today, and worked some on improving the 72MHz ASC sensing matrix (Hang will comment with details).  After concluding that we had done as much as reasonable with that work, we decided to try walking the PRC spots to see if we could find an alignment that had better sideband buildups.  This is when it all went wrong....

I was thinking that we could use the ISC_LOCK states that are meant for moving the PRC spots (you move a specified slider, eg. IM3 for moving the spot on PRM, and the script moves other sliders to make the cavity axis only move the spot on the chosen mirror.)  But, that required taking the ISC_LOCK guardian out of the Paused mode.  And, I hadn't already selected the PRM_SPOT_MOVE state, so we ran the ISC_LOCK DOWN state.  One of the things that this does is request the TCS CO2 lasers to go to the PREHEATING state.  Since TVo and Danny turned the CO2 lasers on earlier today (and at the time confirmed that 0W were being injected into the chambers), this preheating state was able to start sending several hundred mW to each of the ITMs.  At some point we lost lock after touching a few of the alignment sliders, but then have not been able to lock DRMI with good buildups since then.  After about an hour, I realized that the CO2 laser power was one of the things that had changed with the ISC_LOCK DOWN state, and requested that the CO2 lasers' rotation stages send 0W into the vacuum.  There really shouldn't be anything else in there that affects the alignment. 

However, even after more than an hour or so, we still cannot lock DRMI with good sideband buildups.  We have gone back to the witness sensor positions for all the optics for several different times when we had good DRMI locks both this afternoon and Hang's locks yesterday (these are all pretty similar to one another).  When we do this, we see some really bad pitch modes flash on the AS AIR camera.  We are able to get POPAIR_18 values of about 25% of what we had been achieving earlier this afternoon (POPAIR_B_RF18_I_NORM_MON of only ~8 counts rather than the ~32 we were getting earlier), but not more than that. 

It's very unclear to me why we can't get better alignment right now.  I'm sure there's something obvious that I'm missing, but I don't know what.  At this point, I think Hang and I agree that it makes sense to let the PSL team do their work, and then once we have the laser back we can open up the Xarm beam tube, and really set our input pointing to that (we didn't finish doing this during last week's peek), and go from there.