(We tried to post this entry during last night, it appeared on my local session of the logbook, but in fact the post did not work).
The goal of the afternoon shift was to find the longitudinal position of SDB1 (Z) that minimizes the CMRF.
At the beginning of the shift, Maddalena commented the engagement of the BS_TY_SET loop in ITF_LOCK.py.
Then there were several unsuccessful lock trials, two unlocks happened right after reaching CARM_NULL_1F. It was then decided to cancel out the last step performed on the NI DAS around 15h20 utc.
While the ITF was in LOCKED_ARMS_BEAT_DRMI_3F, we saw that the SDB1 bench was moving (the drift control was not working). The galvo loops of B1p QD were also open so we closed them manually at 15h18m42-UTC. After this action, the drift control of SDB1 was back in operation.
After several unsuccessful attempts to lock the ITF finally reached a stable lock in CARM_NULL_1F at 16h37 utc.
ITF locked in DC readout at 16h56m30 utc but we unlocked shortly after at 16h57m06 utc during the transition to Low Noise 1.
DC readout reached again at 17h32m10 utc, but ITF unlocked again at 17h34m14 utc during the transition to Low Noise 1. The ISC team noticed the presence of an oscillation on BS_TX at 275 mHz. For safety they are disabling the full bandwidth control of BS for the next relock.
Noticing that the B1p 56 MHz side bands were very unblanced, an offset was added on MICH to improve the balancing of B1p side bands.
It was then possible to reach DC readout at 18h50m05 utc. and Low Noise 2 at 18h52 utc but ITF unlocked at 18h55m18 utc.
DC readout at 19h57 utc and Low Noise 2 at 19h59 utc. Low Noise 3 reached at 20h26 utc.
The BS_TY_SSFS_LF_Q_ENBL was disabled when arriving in Low Noise 3 (because it had been renabled before for a few min), and the offsets were cancelled to bring BS_TY_INPUT back at 0.
We then moved the SDB1 bench along Z (starting from initial position: SDB1_LC_Z = 3890 um, Sa_OB_F0_X = 2599 um).
We performed steps of 100 um on F0_X, and we adjusted the bench TX offset in parallel by doing steps of -2 urad per 150 s, for each step of 100 um of bench displacement.
We stop at 22h43 utc at SDB1_LC_Z = 960 um, Sa_OB_F0_X = -900 um which seems to correspond to a zero on the B1s signal demodulated at 491 Hz. We take quiet data until 23h06 utc, unfortunately the DCP was only getting worse.
Fig.1 shows the scan of the SDB1 bench longitudinal position and the period of data when we stabilized it at SDB1_LC_Z = 960 um. Data will be analyzed offline.
Fig.2 shows the scan of SDB1 in the opposite direction towards the standard position. The ITF unlocked at 23h49 utc.
After the unlock we restored the bench at its standard position and re-enabled the BS_TY_SSFS_LF_Q loop in ITF_LOCK.