Thomas Vo, Jenne Driggers, Sheila Dwyer, Daniel Brown, Alexi Ciobanu, Georgia Mansell, Terry McCrae

Today we had a chance to lock the IMC.  

• There were some settings in the MC suspensions that were incorrectly saved in the SDF snap files.  We don't know why these were updated.  Jeff K went through the MC sus, IMC ASC, and LSC SDFs and compared them to the files at the end of O2 to make sure we understood the changes there. We also talked with Dave Barker about developing some kind of tool that lets us look at what changes have been made to SDF files. 
• We reduced the gain by 4dB to avoid the very small gain margin that we had with our usual IMC UGF of around 45kHz.  We think that this small gain margin could be due gain peaking in to the FSS loop, which Peter K had warned us was not remeasured since the 70W amplifier and possible alignment changes in the ref cav path (41156). 
• We are using Jenne's cleaned up guardian code, (41169), which needed a little bit of debugging but seems to be working.  We have used a few of the ALIGN_IFO states, but not actually locked any cavities. 

After the IMC was locking reliably, we briefly looked at PRX.  We were confused for a while because the BS oplev damping was on and driving the suspension an awful lot.  After this was fixed Alexi roughly aligned PRX, and we changed to single bounce.  Using the alignment settings from 40463, we put excitations on SR3 pitch and yaw and can see the beam on the SRM camera some of the time.  We went to HAM6 briefly to look for the beam but didn't find it.  A more careful job of alignment will need to be done tomorrow or the next time we get a chance.