A simple microwave component for the vacuum window protection in an ECR ion source for ion beam processing

The main drawback of ECR ion sources for industrial applications is the high vulnerability of the vacuum dielectric window, when located in the line of sight of the plasma. We present the study of a simple microwave component consisting in a metallic diaphragm in the form of a thin rectangular resonant slit associated with a differentially pumped buffer waveguide dedicated to the window protection. This device substantially improves the performances of the source. A microwave power as high as 700 W could be efficiently transmitted through a slit height of only 1 mm cut in a 2 mm thick stainless steel plate