Title: ACCESSIBILITY OF LOWER HYBRID WAVE IN TOKAMAK AND STUDY OF FREQUENCY AND MAGNETIC FIELD EFFECTS ON ACCESSIBILITY
Abstract: With due consideration to dispersion relation of cold plasma and applying re- sonance condition to a desired root of dispersion relation for lower hybrid heating, lower hybrid frequency is achieved. Then accessibility condition is resulted from confluence of tow roots. Effects of frequency and magnetic field parameters of applied wave on the ac- cessibility are presented in this paper. A scheme for producing a steady state toroidal current using intermediate frequen- cy lower hybrid waves (f ~1GHz) was first proposed by Fisch in 1978. The idea was to lunch waves with high phase velocities which travelled preferentially in one direction around the torus. Upon Landau damping on a population of super thermal electrons, these waves would then transfer momentum and energy to the particles generating a net cur- rent. In lower hybrid current drive, energy and parallel momentum are transferred from externally-excited waves in the plasma to resonant electrons via Landau damping. Controlled thermonuclear fusion in a Tokamak may be attained by heating the plasma with Radio Frequency (RF) waves of neutral beams to temperatures above those achieved by Ohmic Heating; RF heating of the plasma in the lower hybrid range of frequencies (0.5-5 GHz) is a possible method for a practical and efficient heating scheme. Lower hybrid waves are predicted to damp on the ion population at the location near the lower hybrid resonance in the plasma. Direct heating of the ions is considered desirable because it is the ion that un- dergoes fusion and in most present Tokamaks the ion temperature is lower than the electron temperature by a factor of 1.5 to 3. Furthermore, in present day devic- es, the ion energy confinement time is generally longer than that for electrons. In- crement of plasma energy by ion heating will be more efficient than by electron heating if the absorption efficiencies on the two populations are comparable. Elec-
Publication Year: 2010
Publication Date: 2010-07-01
Language: en
Type: article
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