DESIGN AND INVESTIGATION OF A MICROWAVE PLASMA CATHODE

The physical consideration, design, and characteristics of a compact m icrowave plasma cathode are expounded in this paper. The impedance mat ching is calculated to improve the microwave transmission efficiency. The influence of the magnetic field on the discharge property and the extracted electron beam current is investigated. The off-resonance dis charge mode (a non-ECR discharge mode) is put forward, in which the ma gnetic field is bigger than 875 G in the discharge chamber. The depend ence of the extracted electron beam current on the extraction voltage, the input microwave power, and the operation pressure is described. T he 2.45-GHz microwave power is transmitted to the cathode via a coaxia l line. The permanent magnets made from NdFeB are used to excite the m agnetic field and the magnetic induction of 800-2600 G can be produced . This cathode can obtain the electron beam current of up to 500 mA at the input microwave power of 30-60 W, with N2 used as the support gas .