Peter K, Sudarshan, Gabriele

All the eight photodiodes are now acquired with the temporary break out box, allowing us to measure the direct output of the transimpedance. 

We could finally find what we believe is the real beam, since we got high power on all photodiodes and also on the quadrant. However, we've not been able to find a position that simultaneously center the QPD and maximize all the photodiode signals. We can either center the QPD or maximize one or few of the photodiode signals.

For reference, we have now

QPD = 22000 cts, 13 V

PD1 = 4170 cts = 2.54 V = 2.1 mW
PD2 = 4500 cts = 2.75 V = 2.7 mW
PD3 = 4620 cts = 2.81 V = 2.3 mW
PD4 = 5000 cts = 3.05 V = 2.5 mW
PD5 = 4840 cts = 2.95 V = 2.4 mW
PD6 = 4320 cts = 2.63 V = 2.2 mW
PD7 = 5120 cts = 3.13 V = 2.6 mW
PD8 = 5000 cts = 3.05 V = 2.5 mW

There is an excursion of about 20% from the minimum to the maximum. For sure, the present position does not correspond to one that minimize the jitter to RIn coupling for each diode separately. We tested that adding a slow 1 Hz modulation  in pitch or yaw on IM3 does introduce a fluctuation in the PD signals. The effect is particularly large in yaw, and much smaller in pitch.