Avalanche photodiodes operating parameter optimization for the Frascati Tokamak Upgrade Thomson scattering system

Measured figures (linearity, avalanche gain, frequency response, and noise) of the avalanche photodiodes (APD) detectors used on the FTU Thomson scattering system (FTU-TS) are reported. This investigation on the APD figures is motivated by the necessity of knowing their values over a wide range of input signals, and also of checking the validity of McIntyre model of APD noise, since using this model the experimental signal-to-noise ratio is calculated. From the noise analysis, a method of optimization of the detection system sensitivity is derived, leading to the optimization of the signal-to-noise ratio over the entire FTU-TS system. copyright 1997 American Institute of Physics