AIP Digital Archive
Electrical Engineering, Measurement and Control Technology
A microwave plasma (MP) cathode for ion sources has advantages of a long lifetime for reactive gas, and a capability of a high-current electron emission of several amperes. This article describes a new MP cathode, in which a convergent magnetic field is formed at an electron emitting aperture in order to improve the working gas efficiency, that is the decreasing of the gas flow rate (Qeff) to obtain the electron emission current of 1 A. By applying a magnetic field (∼3 kG), the Qeff was decreased to 1/5 to 1/10 of that in the conventional MP cathode, and a high current of oxygen ion beam of 62 mA in a high vacuum (1.8×10−5 Torr) system was successfully obtained. Further improvements are expected by changing various parameters.
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