Kuwahara, Ohishi, Takahashi

We measured the calibration factors of the optical levers at XY end mirrors from the mirro tilt [rad] to the output signal.

As the oupput signal, we adopted the normalized output counts (Counts/SUM).

The method was according to http://klog.icrr.u-tokyo.ac.jp/osl/?r=569.

First, we measured the factor from beam spot positon on QPD to the output signal (=dP/dx, x is position, P is normalized output), by displacing the horizontal(X) or vertical(Y) position of the QPD on the micrometer.

The matrix components for converting QPD signals into Yaw or Pitch signals at Yend optical levers had not been set, so we set the same values as Xend matrix shown in Fig. 1.

Second, we measured the length between QPD and mirror, which was  L=1473(7) mm (1150(5) mm from mirror to chamber window by CAD + 323(5) mm from chamber window to QPD by ruler).

Then the calibration factor of the optical levers are obtained as dP/dθ=2L*dP/dx because of the simplest optical levers.

The results at Xend Yaw(X), Xend Pitch(Y), Yend Yaw(X), Yend Pitch(Y) are respectively shown in Fig. 2-5, and 

dP/dx:   -2.69(5) (out/sum)/mm,  3.05(5) (out/sum)/mm,  -2.24(2) (out/sum)/mm,  2.47(3) (out/sum)/mm,

dP/dθ:   -7.92(15)e3 (out/sum)/rad,  8.99(15)e3 (out/sum)/rad,  -6.60(7)e3 (out/sum)/rad,  7.28(9)e3 (out/sum)/rad.