Noise Width (10/28/02)
The noise width is about 8 channels FWHM with no detector and increases with increasing APD bias.
A noise of 8 channels corresponds to 0.8fC based on the gain calibration for this setup.
The increase in noise with bias is partially due to leakage current but leakage current does not
appear to increase as sharply with bias as noise does.
The APD response to light pulses shows considerably more variation than the amplifier
noise alone. The light pulse amplitude was adjusted to keep the peak
around channel 150 (about 16fC output pulse from the APD).
Since the APD gain increases with bias, the light pulse amplitude is
much lower at higher bias.
Setup:
puadj = 1.6
sh1adj = 1.4
preadj = 1.6
th1adj = 3.0 30K (disable disc 1)
th2adj = 1.9 (convert all)
dlyns = 550
zeroadj = 1.1