Performance, radiation damage and future plans of the BaBar Silicon Vertex Tracker

The BABAR Silicon Vertex Tracker has been in operation for four years at the PEP-II electron-positron storage ring. During this time the SVT modules have accumulated a radiation dose up to 2 MRad. We study the degradation in the performance of the SVT due to this accumulated dose which is highly non uniform across the detector and also within the single crystals. To extrapolate the performance of the detector to the future we study separately the effect of the irradiation on silicon wafers, front end integrated circuits and on a complete detector module under controlled radiation conditions, using a ⁶⁰Co source and a 0.9 GeV e- beam. We compare the results to the data from the SVT. In particular we show the dependence of the charge collection efficiency on the radiation dose even when a small stripe of the module is irradiated up to bulk type inversion. Since the modules that lay in the plane of the beams will suffer significant radiation damage, we will describe our plans for their replacement in 2005 and for the operation of the SVT through the lifetime of the BABAR experiment.