We did a TCS tuning test at 50W starting at 6:56 UTC. The CO2X power was decreased from the nominal 400 mW to 0. During the test, we have monitored the frequency and intensity noise couplings to DARM by injecting broadband noise. I will analyze and post the results tomorrow, but it seems like that a small CO2X value is better fore laser noise couplings.
During the test, we tried to compensate for varing optical gain by changing the CAL-CS sensing gain setting. There was a period where we had a 80 Mpc range which was due to uncompensated change in the optical gain induced by the thermal transient. However, we believe that the range will be better with the fine tuned CO2s. Unfortunately, the laser tripped shortely after the test. We did not get a chance to examine the improvement.
Looks like the diode chiller tripped this time. Not sure why. The Epics alarm was triggered. More later. For reasons unknown at the moment, the diode chiller suffered a temperature transient at around 1:20 am local time. Most likely the transient triggered a chiller error because it exceeded the maximum temperature limit of the chiller. Chiller room temperature plot is also attached. Around 6 am (local) Tuesday morning, the diode chiller temperature took a dive to 18.5 degC on average with excursions as low as 17.9 degC. The diode chiller low temperature limit is set to 18 degC. So this would explain why the chiller tripped.