We also scanned the TY position of SPRB in low noise 1 in order to better check the "edges" of the photodiodes plateau (see Fig.1). Although not visible in Fig.1, we could see the power on PD2 starting to decrease after doing 2 or 3 more microrad in the negative direction. Thus Fig.1 shows almost the whole plateau of PD2.

After this scan, we set the TY position of the bench at -588 urad (position reached at 11h48m30 on the plot) as it is near the center of the plateau both on the DC and 112 MHz channels of PD2. In order to set this new position with the bench drift control engaged, an offset (-7V) was added to the correction of the galvanometer mirror placed in front of the QD2 quadrant.

The scan of SPRB in TY performed on Nov 21 allows to check what would be the best setpoint to have the PD1 photodiode well centered. Looking at the blended signal of PD1 (Fig.1 and Fig.2) on can see that the middle of the plateau is around TY=-595 urad. The bench was adjusted to -588 urad in order to optimize the centering of  PD2. Thus the bench setpoint should be adjusted by -7 urad in order to have the best centering on PD1 (with the current position one can see from Fig.2 that the power on PD1 is ok, but there is not a lot of margin with respect to the edge of the plateau).