Mitsuyasu Yatsuzuka

Cross-Field Current-Driven Electrostatic Instabilities and Plasma Heating in a Counterstreaming Electron-Beams – Plasma System

Experimental studies are presented of the wave characteristics and associated plasma heating in a system composed of two counterstreaming electron beams and a longitudinally magnetized inhomogeneous plasma. Such an injection of two beams makes the plasma potential strongly negative, and produces the cross-field current. Three types of electrostatic instabilities are excited by the cross-field current, i.e., lower-hybrid instability, ion-cyclotron harmonic instability, and modified ion-cyclotron instability. As the latter two instabilities grow strongly, nonlinear wave mixing develops between them. Corresponding to the rapid growth of these instabilities, substantial ion and electron heating takes place in the direction perpendicular and parallel to the magnetic field, respectively. Heating mechanism of ions is also discussed, and it is found that the energetic ion production is attributed to the lower-hybrid turbulent heating.

Plasma Heating in the TP-M Device by the Injection of a Spiraling Electron Beam

The interaction of a spiraling electron beam with an inhomogeneous magnetoplasma is studied experimentally in the Nagoya TP-M device. There appears strongly an azimuthal stream of electrons (i.e., crossfield current), which excites electrostatic instabilities near the lower-hybrid frequency and the ion-cyclotron frequency. Corresponding to the growth of these instabilities, plasma heating takes place rapidly. The heating may be interpreted as the crossfield-current-driven lower-hybrid turbulent heating.