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AdV-INJ (Input Mode Cleaner cavity)
de rossi - 17:14 Monday 21 January 2019 (44457) Print this report
some IMC unlocks analysis

During the week-end the INJ was left in standalone. I analyzed the different IMC unlocks, finding 3 different behaviors.

- the first kind of unlocks occured this morning and is characterized by the saturation of the PSTAB correction (see plot 1 as an example). When saturation occurs, it makes a glitch on the error signal at a frequency of 500 Hz (well below the PSTAB UGF which is around 70 kHz)

- a second kind of unlocks are the so called fast unlocks, for which the IMC power drops very quickly without clear cause. An example is given on plot 3. However it has to be noticed that some glitches just before the unlocks are present on the IMC error signal and on the EOM correction (see plot 4). They maybe occur from time to time, and sometime the system cannot stand them and unlocks. Another feature to take into account, even if the link is no proven, is the behavior of the SL pumping diode 1 , which seems quite glitchy (see plot 5). This suggest that fast unlocks might be caused by different sources.

- the third kind of unlock occurred only once and was due to a misalignment of the IMC cavity (see plot 6)

GPS (UTC time) cause of the unlock
07:18:20 saturation of the PSTAB correction
07:27:10 saturation of the PSTAB correction
07:34:50 saturation of the PSTAB correction
07:35:30 fast unlock
01:44:00 fast unlock (glitch EOM corr)
02:57:00 misalignment of the cavity
18:36:40 fast unlock
18:36:55 fast unlock
19:14:37 fast unlock
19:16:36 fast unlock (glitch SL pumping diode 1)
19:17:15 fast unlock (glitch EOM corr)
11:16:50 fast unlock
11:21:40 fast unlock
10:58:15 fast
07:15:50 fast
07:22:59 fast
07:23:47 fast
Images attached to this report