In the last days many glitches seem to come from the PSTAB. We then performed two actions:

- PMC realignment, as already observed and suggested by F. Cleva (#47533).

- PSTAB gain adjustment. We injected a line on the "perturb" input of the PSTAB locking electronics and monitored at the scope the amplitude of the error signals before and after the perturbation. We then adjusted the frequency of the injected line in order to have them of the same amplitude: this frequency is a good estimation of the UGF. It was 120 kHz, and by lowering a bit the gain we brought it at ~ 80 kHz (the corresponding position of the potentiometer is 9 o'clock).  The first plot is a comparison of the current PSTAB err signal (blue) with the one we used to have before Oct 22nd (#47250), when we lowered the power on the photodiodes.

From plot 2 we can observe that the error signal is now much less glitchy, and also from the omicron scan the glitches at 1 kHz seem to have disappear (plot 3).