Lower-hybrid-heating data on the Wega experiment revisited, using ion-stochastic-heating and electron-Landau-damping theories

Abstract

Previously obtained data on the Wega tokamak by lower hybrid heating (f = 500 MHz; PHF = 130 kW) are re-visited in the light of recent theories on ion stochastic heating and quasi-linear electron Landau damping. It is possible, with the help of these theories, to correctly estimate the fast-ion mean energy, the HF power density coupled to the ions and that coupled to the electrons. The values of the parallel index of refraction, N‖, which are necessary to obtain a good quantitative agreement between experiment and theoretical estimates, are the same for ions and electrons, although higher than expected.

Quasi-linear theory calculation of ion tails and neutron rates during lower hybrid heating in Alcator-A

“…In the following, we assume quasi-linear theory to be valid and employ diffusion coefficients similar to those of Karney [9]. Quasi-linear theory has already been applied to the Wega experiment and was not found to be inconsistent [12]. Here, we first assume perfect ion confinement, and calculate ion tails and bulk heating in Section 2.…”

Quasi-linear calculation of ion tails and neutron rates in a D-T plasma due to lower hybrid waves

“…Such ion tails are predicted by the quasi-linear theory of Karney [6]. It has been shown that this theory is not inconsistent with the ion tail observations of the Wega experiment [7]. Furthermore, a Monte Carlo quasi-linear ion heating code has shown consistency between its results and the Alcator-A RF-produced ion tails [8,9] .…”

“…However, this class of instability is characterized by wavelengths that can be comparable to the Larmor radii of the ionic species of the plasma. Therefore, kinetic modifications to the MHD predictions can be very important [6][7][8][9]. Significant stabilizing effects have been reported from finite diamagnetic drift frequency [ 10] and other kinetic effects [ 11 ] in model tokamak equilibria with a large-aspect-ratio circular cross-section.…”

A Magnetic Force Microscope Using an Optical Lever Sensor and Its Application to Longitudinal Recording Media

“…Such a concept eases the technical constraints due to the very large number of waveguides foreseen for future large tokamaks. [12]). [11,12].…”