A new gas attenuator system for the ID17 biomedical beamline at the ESRF

On the biomedical beamline ID17 at the ESRF a gas attenuator system has been installed to complement and protect the standard solid state attenuators (graphite, Al and Cu) against fatigue and damage due to the very high heat load from the beamline's wiggler source. This series of attenuators defines the flux (dose rate) and the X-ray beam spectrum for the Microbeam Radiation Therapy (MRT) research at ID17 which is currently under development towards clinical application. For this, the attenuators at MRT will be crucial elements to guarantee beam- and dose rate characteristics and the new gas attenuator will become a radiation therapy safety device. The installed gas attenuator and its test results will be presented.