An imaging photon counting intensified CCD for high speed photometry

The scientific performance evaluation of a photon counting imaging system i s presented. The detector is constituted by an ICCD camera with RbTe photoc athode (optimized for UV radiation), and dedicated electronics for the acqu isition and analysis of the events. For each photon event on the CCD, a rea l-time centroid calculation is performed, in order to reach spatial resolut ion down to 25 mum FWHM. The system has been tested using the 182 cm telesc ope of the Asiago Observatory. A standard stars field through U Johnson fil ter, and the Crab pulsar (PSR 0531+21) were observed. From the photometric data, relative magnitudes of the standard stars have been derived, showing a good linearity of the detector in the range of flux under consideration, as expected from previous laboratory measurements. The pulsar's data have b een processed by FFT and epoch folding techniques to test the detector's ti ming performances in the highest resolution mode (4.512 ms). These observat ions show that a space resolved time analysis of periodic sources can be pe rformed with 10(-7) s accuracy.