After the BS istallation, I proceed with the implementation of the local controls as it was done for the PR mirror in July.

OPTICAL LEVER

As a first thing, I restored the opltical lever (see first attaced picture). In order to have the  PSD voltage sum <15, to avoid saturation, I put a filter in the laser path to  reduced the power.

The power reaching the PSD is about 340 mW which corresponds to a voltage sum of 14.8 V.

TRANSFER FUNCTIONS AND CONTROL LOOPS

1) I have measured the mechanical transfer function of the mirror when exciting yaw and pich respectively (plot pag 1 and 2 of the attached document).

2) I have measured the open loop transfer function of the two degree of freedom (plot pag 3).

3) I have closed the two loops and plotted the comparison between the calibrated spectrum when the loops are open and when they are close (plot pag 4 and 5).

CALIBRATION

In order to calibrate the signal I assuemed that the PSD had the same calibration factor measured for the PSD of the same type used for the PR (see entry 276) (maybe this has to be verified..)

I follewed the same procedure explained in entry 276.

n_cal = 0.0071+/- 0.0002  (normalzed calibration)

arm = 0.60 m +/- 0.05 m  

V_sum = 14.8 V

Cal_tot =  n_cal/(2*arm*V_sum) =  (3.04 +/- 0.26 ) e-4 [1/V]