Study of Charge Clusters in the ATLAS SCT

Cluster studies for the SCT are presented in this poster. The depletion depth of the sensors is measured using cosmic data taken between 2008 and 2009. Two different methods are explored for runs with and without the solenoid magnetic field at different bias voltages. When the magnetic field is zero, the results are consistent with the expected values. If the magnetic field is present, the depletion depth is measured indirectly via the slope of the average cluster size as a function of the local incidence angle. A comparison between 900 GeV collision data and MonteCarlo is also shown where some discrepancies have been observed in the cluster size distribution. This is an indication that the SCT digitisation model needs to be tuned.