Sheila, Georgia, Jenne

Today we took some commissioning time to try to increase the input power.  The increase in input power went fairly well, but we had many locklosses due to problems unrelated to power up, more likely related to Tuesday maintence.  In total we spent about 3-4 hours today commisioning, although the observatory mode was set to commisioning the entire time. 

Increasing power:

• We were able to increase the power to 40W requested input in the adjust power state without many problems, although we haven't had a stable low noise lock yet with the increased power.  
• We made some effort to make sure that it would be easy to revert the changes we made if necessary, and make it easy to come back to this effort another day just by changing the requested power for low noise in lscparams.
• As we increase the input power from 35W to 40W, the POP18 build up drops from ~50 cnts to eventually settle just below 40 counts.  To keep the PRCL ugf at around 50Hz, we need to increase the PRCL digital gain from 16 to 30.  We added a decorator to ISC_library that watches the value of POP18 and adjusts this gain in two steps as we thermalize, and we added this to several of the states that immediately follow the power increase.  This seems very similar to the expirence of increasing the power from 25W to 30-35W in December.  After some changes to TCS and spot positions we were able to prevent the PRCL gain and the POP18 from dropping as dramatically then.  For now it seems OK to digitially compensate for the change in optical gain until we have a chance to improve the build ups. 
• The CARM ugf stays pretty close to 7kHz in these steps (It doesn't get increased to 14kHz until the LASER_NOISE_SUPPRESSION state). 
• Georgia changed the POWER_30W state to MAXIMUM_POWER, and it is written so that all we need to do to change the requested power from 35W to 40W is to change the NLN_POWER in lscparams.
• We made some slight adjustments to the MICH and SRCL gains in LOWNOISE_LENGTH control based on ugf measurements: MICH gain is increased by 10%, SRCL gain 55%.   These are set based on the power request in lscparams.
• We had no difficulties with the noise reduction states after powering up, until we tried to reduce the 9MHz modulation depth.  This seems to have created an ASC instability, which caused enough noise that we started to saturate the ASC REFL45 sensors.  We reduced their whitening gain by 6dB and added 6dB digital filters, but we have not been able to relock since then because of other prolems.  Because we have been having unrelated ASC problems, we reverted the change to be sure that nothing we did today could be the cause of the locking issues. 
• Our rough plan for the next time that we are able to try going to 40W would be to sit and let things thermalize without reducing the 9MHz modulation depth. There we could check the phasing of the REFL WFS, measure the ASC sensing matrix, and perhaps try tuning CO2s to improve the POP18 build ups.

Other problems:

most of our locklosses today were unrelated to powering up, we lost lock twice for reasons that were related to our commissioning efforts, the rest of our many locklosses seem to be related to other problems.  We have had MC1+3 T2 osem glitches 3 times today, 49257 the first two times caused locklosses, and the third time we were able to stay locked.  

We also have had many similar locklosses in the states where we engage ASC and transition to DC readout before powering up.  We don't understand this, and the problems seem to have started yesterday.  

• We saw that the M3 picomotor which was moved yesterday (49238) wasn't set quite back to the original location according to the counter (the counter isn't a reliable way of knowing where the pico is, but it is the best thing we have).  We tried to undo this move by running the green WFS and camera, then opening the loops and moving the pico back to its original counter position (moving it by about 130 counts down).  After that we relocked the arm in green, and ran a complete initial alignment.  According to the sliders and top mass drift monitors this brought our alignment closer to what it was before maintenance day yesterday, but not all the way back. 
• We noticed that both SRC2P and INP1P were not bringing their error signals to 0 when we are engaging the ASC, so we have increased their gains, SRC2 will be reset latter in the guardian but is left with a factor of 3 higher gain for the ASC engagement and power ups.  For INP1 we have increase the gain by a factor of 10, and this will stay increased in full lock.  
• In our most recent locking attempt we phased AS72 after the ASC came on but before the soft loops were engaged.  We opened the SRC1 loops and adjusted the SRM alignment by hand, then adjusted the phases of AS72A to zero the Q signal in each quadrant.  This resulted in better POP18 and POP90 build ups, and we were able to get through the following steps.  We will see if this has fixed the problem or if we just got lucky this time.