Development of a fast H1 trigger using silicon pad detectors

Based on the low noise performance and fast timing response of crystalline semiconductors, a silicon pad detector telescope has been developed for a first level trigger on electrons scattered into the backward region of the H1 detector. The trigger system design is described and beam test results are presented for the Backward Silicon Tracker, which was installed in 2001 to be operated in H1 after the HERA upgrade.