The HERMES silicon project—the radiation protection system

The HERMES-detector has recently been upgraded with a silicon detector called the Lambda Wheels. This is the first detector following the interaction region. It consists of two disks of silicon detectors close to the beamline. This location makes it vulnerable to increased radiation levels which may be caused by beam instabilities. The Lambda Wheel detector, therefore, contains a system to detect these instabilities. This additional system triggers a kicker which dumps the HERA-lepton beam when the radiation level becomes too high. ontribution describes the radiation monitor which consists of two sets of three ionization chambers each, and the data-acquisition system which reads them out. The system has been installed and is operational since the summer of 2001. The HERA-accelerator was being commissioned after an upgrade during this time and several kinds of beam instabilities were observed with this protection system. The characteristics of some events will be described.