First operation of the flash machine protection system with long bunch trains

The linac-based free electron laser facility FLASH1 at DESY Hamburg is designed to transport an electron beam with an average power of more than 50 kW. To avoid seri-ous damage to accelerator components, a fast active ma-chine protection system (MPS) stops the production of new bunches if hazardous machine conditions are detected. This paper gives an overview of the MPS topology and its subsystems. Furthermore, we present results from the commissioning of the fast beam interlock system that has for the first time allowed to operate the accelerator with macropulses of up to 600 bunches