Showing papers by "Sanae I. Itoh published in 1993"
TL;DR: In this article, the averaged force of radio frequency (RF) waves acting on each species of a plasma can be divided into a resonant force and a nonresonant one.
Abstract: Current drive via nonresonant interaction between radio‐frequency (rf) waves and plasma is studied. The averaged force of rf waves acting on each species of a plasma can be divided into a resonant force and a nonresonant one. A part of the nonresonant force cannot be expressed by a gradient of a scalar potential and remains after integrating along the direction of the force. This force mainly acts as an internal force among plasma species and the net momentum input from the wave to the plasma is usually small. This process is not included in the conventional current drive schemes but is associated with the rf wave helicity injection. Quantitative analysis using a one‐dimensional kinetic wave code is applied to waves in the ion cyclotron range of frequencies and low‐frequency Alfven waves in a large tokamak. The driven current is estimated taking account of the effect of the toroidally trapped particles. The spatial profile of the forces acting on electrons and ions as well as the driven current are obtained. The parameter dependence of the current drive efficiency on the wave number, the plasma density, the temperature, and the toroidal magnetic field is compared with the estimate based on a local analysis.
16 citations
TL;DR: In this paper, the authors analyzed the ion motion caused by sawtooth crash in the framework of the magnetic stochasticity model of the saw-to-oth crash and showed that the average current profile changes much more slowly than the pressure profile after the onset of the crash, so that inhomogeneity of the parallel current along the field line is generated.
Abstract: Turbulent ion motion caused by sawtooth crash is analyzed in the framework of the magnetic stochasticity model of the sawtooth crash. The average current profile changes much more slowly than the pressure profile after the onset of the crash, so that inhomogeneity of the parallel current along the field line is generated. This causes a perpendicular current with a short scale length, leading to the ion cross field motion.
1 citations
TL;DR: In this paper, the relation between RF-driven current and wave helicity is analytically and numerically studied for a tokamak plasma, and the helicity conversion ratio from the wave to the plasma is discussed and examined for the waves in the range of ion cyclotron frequency in JT-60 plasma.
Abstract: The relation between RF-driven current and wave helicity is analytically and numerically studied for a tokamak plasma. The helicity conversion ratio from the wave to the plasma is discussed and numerically examined for the waves in the range of ion cyclotron frequency in JT-60 plasma. The wave propagation equation which includes kinetic effects is solved as a boundary-value problem with one-dimensional inhomogeneities. Both the RF helicity-driven current and the RF momentum driven current are calculated. It is shown that the efficiency of the current drive by the wave helicity is small compared with the conventional scheme for the fast wave excitation of the present-day plasma parameters.