Kakuyūgō kenkyū

The boundary conditions for heat flow in ohmically heated tokamaks are examined by using a simplified model. The analysis shows that the hot plasmas of a certain parameter, density of-10¹⁹ m^-3 and confinement time of-10 msec are compatible with the boundary condition.

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An experiment is performed to study the interaction of a high power microwave pulse with a magnetized dense plasma. A delayed emission appears after the complete termination of a pumping microwave pulse when the frequency of the pumping wave is equal to the harmonics of the cyclotron frequency and is near the plasma frequency. Three types of the delayed mission (type I, II, III) are observed, depending on the experimental conditions. Type I delayed emission is characterized by the frequency spectrum with sharp peaks at cyclotron harmonics (mf_ce m= 1, 2, ..), type II with broad peaks between (m+1/2) f_ce and (m + 1) f_ce and type III with broad peak between 0.8 fce and fce. Main properties of these phenomena are explained in terms of anomalous power absorption at cyclotron harmonic resonances and excitation of electron plasma waves by an anisotropic electron velocity distribution. Each type of the delayed emission can be triggered artificially by a sudden decrease of cold back ground plasma density and is suppressed by an increase of cold plasma. It can be also triggered by a pulsed electron beam.

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