Oli, Camilla, Sheila, RyanS
It was pointed out (84972) that our new SRCL offset is too big at the beginning of the lock, affecting the calibration and how well we are squeezing. Camilla had the idea of taking the unused-but-already-set-up THERMALIZATION guardian and repurposing the main state so it steps LSC-SRCL1_OFFSET from the LSC-SRCL1_OFFSET value at the end of MAX_POWER to the official offset value given in lscparams (offset['SRCL_RETUNE']). This stepping starts at the end of MAX_POWER and goes for 90 minutes. Here is a screenshot of the code.
To go with this new stepping, we've commented out the line (~5641) in ISC_LOCK's LOWNOISE_LENGTH_CONTROL (ezca['LSC-SRCL1_OFFSET'] = lscparams.offset['SRCL_RETUNE']) so that the offset doesn't get set to that constant and instead keeps stepping.
To get this to run properly while observing, we did have to unmonitor the LSC_SRCL1_OFFSET value in the Observe sdf (sdf).
Attached is a screenshot of the grafana page, highlighting the 33 Hz calibration line, which seems to be the most sensitive to thermalization. Before, when the SRCL offset was set static, it appears that the 33 Hz line uncertainty starts at about 1.09 and then decays down to about 1.02 over the first hour. With the thermalization adjustment of the SRCL offset from 0 to -455 over one hour, the 33 Hz uncertainty starts around 0.945 and then increases to 1.02 over the first hour. Seems like we overshot in the other direction, so we could start closer to -200 perhaps and move to -455.
We decided to change the guardian so that it starts at -200 before then stepping its way up to -455 over the course of 75 minutes instead of 90 minutes.
With the update to the guardian to start at -200, each calibration line uncertainty has actually stayed very flat for these first 30 minutes of lock (except for the usual very large jump in the uncertainty for the first few minutes of the lock).
This shows the entire lock using the thermalization guardian with the SRCL offset ramping from -200 to -455, The line uncertainty holds steady the entire time within 2-3%!
