Hideo Ikegami

Excitation of obliquely propagating cyclotron harmonic waves

Obliquely propagating cyclotron harmonic waves are excited and their behavior is studied. The waves can be excited within the region that satisfies the condition, ω p 2 >ω 2 -ω c 2 . Contrary to the commonly accepted notion, it is confirmed that the cyclotron harmonic wave is in a propagating mode rather than in a standing mode. The wavenumbers in the direction parallel to the magnetic field lines are determined by the geometrical length of the exciter.

Negative Absorption and Energy Distribution of Hot Electrons in Relativistic Magnetized Plasma

Negative absorption for extraordinary waves by the weakly relativistic electrons with the energy less than 20 keV gyrating in a tenuous plasma confined in a mirror field is studied by the microwave transmission method. Typical amplification factor of approximately 30 dB for the input power of a few milliwatts is observed during both heating period and after-glow. The experimental results are best explained by the relativistic mass effect obtained by Bekefi et al. for the energetic electron plasmas. Further the formation and relaxation of the distribution function of the energetic electrons are studied through the analysis of the temporal variation of the negative absorption. New method of microwave diagnostics for the determination of energy distribution function of energetic electrons in the tenuous magnetized plasma is proposed.

Microwave Diagnostics for the Measurement of Plasma Density in a Cylindrical Metal Vessel

Microwave interference method for the measurement of the electron density of plasmas contained in a metal cylinder is studied theoretically and experimentally. It is pointed out that the interferometer signal through the metal vessel can not eliminate of the cavity mode effect, even if the dimension of the vessel is large compared with the wavelength of the probing microwave. It is concluded that the cavity mode effect can be ignored, if the Q-value of the cavity filled with plasma satisfies the condition Q<2b/λ, where b and λ are the radius of the cylindrical cavity and wavelength of the probing microwave respectively.