Modifying the pumping current of the diode may actually modify the mode hop temperature mid range.
This morning we went in laser to tune the temperature of the crystal of the ML.
We first tried to change the temperature of the crystal looking at the PDH of the slave but it had a very strange behavior (cf plot 1) and we could not get any information from it.
We then tried to keep the SL locked and to look at the correction (PSL_SL_PZT_SLOW) to see when there were unlocked that were not due to the end of the PZT range (about -0.5 V for the lower limit and 6 V for the upper one). See the attached plot and the different temperatures hereafter:
1297424074 15 Feb 2021 11:34:16 UTC (15 Feb 2021 12:34:16 CET)
temp display 30
pzt 0.3
1297424167 15 Feb 2021 11:35:49 UTC (15 Feb 2021 12:35:49 CET)
temp display 28.63
pzt before jump 3V
1297424247 15 Feb 2021 11:37:09 UTC (15 Feb 2021 12:37:09 CET)
temp display 27.26
pzt before jump 5V
1297424330 15 Feb 2021 11:38:32 UTC (15 Feb 2021 12:38:32 CET)
temp display 25.9
pzt before jump 6V
1297424415 15 Feb 2021 11:39:57 UTC (15 Feb 2021 12:39:57 CET)
temp display 24.7
pzt before jump 6V
1297424492 15 Feb 2021 11:41:14 UTC (15 Feb 2021 12:41:14 CET)
temp display 23.4
pzt before jump 6V
1297424583 15 Feb 2021 11:42:45 UTC (15 Feb 2021 12:42:45 CET)
temp display 22.2
pzt before jump 5.5V
1297425244 15 Feb 2021 11:53:46 UTC (15 Feb 2021 12:53:46 CET)
temp display 24.1 (going up with temp)
pzt before jump -0.5V
1297425305 15 Feb 2021 11:54:47 UTC (15 Feb 2021 12:54:47 CET)
temp display 25.5.
pzt before jump -0.5V
1297425305 15 Feb 2021 11:54:47 UTC (15 Feb 2021 12:54:47 CET)
temp display 25.9 (!!!)
pzt before jump 1.5V
1297425415 15 Feb 2021 11:56:37 UTC (15 Feb 2021 12:56:37 CET)
temp display 27.5
1297425461 15 Feb 2021 11:57:23 UTC (15 Feb 2021 12:57:23 CET)
temp display 29.1
We did it in one way and the other, noticed two unlocks that were not due to the end of range of the PZT:
28.6 while going down
25.9 while going up
This is strange, we were expecting more mode hops (cf figure 3)
At the end of the day we took 25.9 as a mode hop and decided to stay 1.3 degrees away from it :
1297425816 15 Feb 2021 12:03:18 UTC (15 Feb 2021 13:03:18 CET)
set to 24.6 degrees.
In the meantime Jean-Pierre explained us how to get a clean scan from the SL rampeauto. We may try again the first method (ie looking at the PDH) to better see the mode hops.
We took advantage of working on the ML to change the monitoring signals that we are acquiring.
The channel PSL_ML_NOISE_EATER_FS is now monitoring the "crystal temperature error signal"
The channel PSL_ML_D2_POWER_FS is now monitoring the temperature of diode 1.
We will update the names soon.
