Jennie Wright, Rahul

Earlier, we have measured the QPD readout per mm to be around 44.1V (in X direction). This afternoon we dithered the input beam (spot size, radius = 200 microns, see LHO alog 85458) in horizontal and vertical direction at 100Hz using the signal generator (amplitude 2V peak to peak and offset 2.5V). This we did after centering the beam on the QPD (output was around 10,500 counts approx.). The output voltage applied on the dither was around 80V. Given below are the results,

Horizontal dithering:-

On the QPD the dither amplitude X (peak to peak) was estimated to be 2.2V, Mean 6.5V

Beam motion estimate X= 50microns

Dither amplitude Y (peak to peak) was estimated to be 1.2V, Mean -355mV

Vertical dithering:-

On the QPD the dither amplitude X (peak to peak) was estimated to be 1.0V, Mean 4.45V

Beam motion estimate X= 20microns

Dither amplitude Y (peak to peak) was estimated to be 1.62V, Mean -7.96V.