Investigation of the charge collection for strongly irradiated Silicon strip detectors of the CMS ECAL Preshower

Strongly irradiated silicon strip detectors of different size, thickness and different design options were tested in a muon beam at CERN in 1999. A charge collection efficiency in excess of 85% and a signal to noise ratio of 6 are obtained in all cases at high enough bias voltage. Details of the charge collection in the inter-strip and the guard ring region and crosstalk between strips were also studied. We find that the charge collection efficiency and the cross talk between strips depend on the interstrip distance.