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

The dynamics of electrons generated in silicon drift detectors is studied using an IR LED. Electrons were generated at different drift distances. In this way the evolution of the cloud in anode and drift directions as a function of drift time was measured. For the anode direction the method of cumulative functions was used to extract the electron cloud profiles. The cloud width was obtained also from measurements of the charge collected on a single anode as a function of the coordinate of the light spot. We present the first report of the experimental measurements of the cloud width in the drift direction extracted from signal waveforms. The evolution of the electron cloud width with drift time is compared with theoretical calculations. Theoretical expectations agree with our experimental results.