A reflector antenna for electron plasma waves

Summary form only given. A linear antenna with a mesh reflector immersed in a plasma was studied in the frequency range where electron plasma waves can propagate. The electron plasma wave appears to be difficult to excite and to be buried in the noise level because it is damped by Landau damping except in a very small region of frequency above the electron plasma frequency. It is of interest to find an antenna which can excite or receive electron plasma waves efficiently. The antenna consists of a straight thin wire with a 4-cm-long and a rectangular tungsten mesh reflector, 3.3 cm in width and 6.3 cm in height, which are connected to the inner conductor and the outer conductor of a semirigid coaxial feed line, respectively. The antenna dimensions are very small in comparison with the electromagnetic wavelength. In numerical computation the method of moments is used, and in order to reduce the computation time the current on the reflector is assumed to flow in parallel with the wire antenna. The measured radiation patterns for electron plasma waves show unidirectional patterns, which are compared with the theory. The measured input impedances of the reflector antenna are in rough agreement with the computed results.<
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