Two dimensional studies of dynamics of electron clouds in silicon drift detectors

The dynamics of electrons generated in silicon drift detectors is studied u sing an IR LED. Electrons were generated at different drift distances. In t his way the evolution of the cloud in anode and drift directions as a funct ion of drift time was measured. For the anode direction the method of cumul ative functions was used to extract the electron cloud profiles. The cloud width was obtained also from measurements of the charge collected on a sing le anode as a function of the coordinate of the Tight spot. We present the first report of the experimental measurements of the cloud width in drift d irection extracted from signal waveforms. The evolution of the electron clo ud width with drift time is compared with theoretical calculations. Theoret ical expectations agree with our experimental results.