J. Kissel

Incrementally crawling along as I build up all the necessary information in order to model the impact of thermalization on calibration during O4, I state here a record of "good" lock acquisitions when the IFO thermalized from "cold" to "thermalized" at 60W PSL input power, and critically, while the eight extra, "thermalization," calibration lines were ON between 2023-07-25 to 2023-08-09. This is a compliment to similar info for 75W PSL input power shown in LHO:69796. 


60W
    UTC Start           UTC Stop            GPS Start     GPS Stop      Duration   Ref. ID
    2023-06-22 04:55    2023-06-22 08:55    1371444918    1371459318    4.00       1
    2023-07-27 23:42    2023-07-28 03:42    1374536538    1374550938    4.00       2
    2023-07-28 20:10    2023-07-29 00:10    1374610218    1374624618    4.00       3
    2023-07-30 02:50    2023-07-30 06:50    1374720618    1374735018    4.00       4
    2023-07-30 20:23    2023-07-31 00:23    1374783798    1374798198    4.00       5
    2023-07-31 09:35    2023-07-31 13:35    1374831318    1374845718    4.00       6
    2023-07-31 18:05    2023-07-31 22:05    1374861918    1374876318    4.00       7
    2023-08-02 07:51    2023-08-02 11:51    1374997878    1375012278    4.00       8
    2023-08-04 02:03    2023-08-04 06:03    1375149798    1375164198    4.00       9
    2023-08-05 12:57    2023-08-05 16:57    1375275438    1375289838    4.00       10
    2023-08-06 07:40    2023-08-06 11:40    1375342818    1375357218    4.00       11
    2023-08-08 21:52    2023-08-09 01:52    1375566738    1375581138    4.00       12

Here "good" means that the IFO thermalized, and then was stable and locked in nominal-low-noise for 4 hours after (typically, undisturbed and OBSERVING). 
The times were established by trending 
    - the lock-acquisition guardian state (H1:GRD-ISC_LOCK_STATE_N) vs.
    - PSL input power (H1:IMC-PWR_IN_OUT16) vs. 
    - Power in the arm cavities (H1:ASC-X_PWR_CIRC_OUT16, H1:ASC-Y_PWR_CIRC_OUT16)
zooming in on each lock acquisition 2023-07-25 to 2023-08-09 to confirm
    - "clean" ISC-LOCK_STATE_N = 600 status for the entire four hour duration, 
    - nothing screwy went on with the laser power (e.g., this is how I found that Jenne had turned ON the ISS 2nd loop on 2023-08-07 which caused a discrete, 2.5 W drop in arm power -- see LHO:72027)

I don't record *all* off the "good" times, but this is the vast majority -- our duty cycle has gotten so good that there were relatively few lock re-acquisitions over these 14 days! 
Thankfully, there are 12 times that were "good," which should be enough to do a similar study of the sensing and response functions a la LHO:70150.

Note that there is still plenty of stuff changing with the DARM loop and calibration spanning these times, namely that
    (1) From 2023-07-20 to 2023-08-03, a bad MICH2DARM feed-forward filter pollutes the 15.1 Hz ETMX UIM calibration line, freezing GDS time-dependent correction factors, which means the values are *frozen* during thermalization -- see LHO:72812, 
    (2) From the start of O4 thru 2023-08-07, we neglected to model the ETMX TST stage electronics correctly, leaving out a 3.2 kHz pole -- see LHO:72879, and
    (3) From 2023-08-04 to 2023-08-29, a bad SRCL2DARM feed-forward filter pollutes the 102.13 Hz calibration line with its impulse response for hours at the beginning of lock acquisition -- see LHO:72868

For future reference -- this list is pulled from T2300297 a greater list of changes throughout ER15 and O4.