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A new type of plasma source, the Microwave Concentrator Stack, presented in this paper is a device of a geometry that can be described as an elliptical cylinder with additional metallic structures for shaping the electric field in its inside. The basic idea is to concentrate the electric field strength of microwaves on one of its focal lines by coupling microwave power into it on the other focal line. Even though the dimensions of the Concentrator Stack are too small compared to the wavelength of the microwaves to assume wave-optics behavior, a pronounced maximum of the electric field intensity is created on the focal line.By placing an evacuated glass tube around the focal line, free-standing plasmas can be generated by the strong electric field. In the low pressure range (10 to 200 Pa), the plasma displays very good one-dimensional homogeneity along the focal line of the Concentrator Stack. At higher pressures the plasma contracts to several ball-shaped discharges, whose positions correspond to the aforementioned metallic structures inside the Concentrator Stack.The electric field distribution was calculated and optimized for various versions of the Concentrator Stack using the finite element software Comsol Multiphysics TM and also measured with PET absorber sheets. Measurements and calculations are in excellent agreement.

Plasma technology is used in a wide field of applications for example for PECD-deposition, activation and etching. In particular microwave enhanced plasmas are very effective for activation of surfaces. Our objective targets are to construct plasma sources for large area application and plasma sources which can be used in a wide pressure regime as possible up to atmospheric pressure. In this presentation two sources for large area and wide pressure range plasma are discussed. They are based on a coaxial coupling of the magnetron and the antenna