Hamiltonian analysis of fast wave current drive in tokamak plasmas

Abstract

The Hamiltonian formalism is used to address the problem of the direct resonant interaction between the fast magnetosonic wave and the electrons in a tokamak plasma. The intrinsic stochasticity of the electron trajectories in phase space is first derived. Together with extrinsic decorrelation processes, it assesses the validity of the quasilinear approximation for the kinetic studies of fast wave current drive (FWCD). A full-wave solution of the Maxwell–Vlasov set of equations provides the exact pattern of the wave fields in the tokamak geometry, consistent with a realistic antenna spectrum. The local quasilinear diffusion tensor is then derived from the wave fields and the driven current density profile, the power deposition profile and the current drive efficiency are computed, including possible nonlinear effects in the kinetic equation. Several applications of FWCD on existing and future machines are given, and the combination of FWCD with other noninductive current drive methods is investigated. Finally, an analytical expression for the current drive efficiency is derived in the moderate to high single-pass absorption regime.

Electron transport and the critical temperature gradient

“…In order to isolate this magnetic topology dependence, experiments were chosen where sawteeth were absent or weak, and the electron heat source was well localized to the core plasma of Tore Supra [12,31]. The electron transport analysis of these FWEH discharges allows an accurate experimental determination of the radial profile of the thermal flux q e .…”

Kinetic theory of plasma waves

“…Details on the orbit topology and its role in describing the wave-particle interaction can be found in [24][25][26][27][28][29][30][31][32]. The action-angle formalism is discussed in [33][34][35][36][37]. Comments on how to solve the relevant set of equations -with a focus on accounting for the realistic geometry -are given in [38][39][40][41][42][43][44][45][46][47][48][49][50][51] while the role of decorrelation is the key subject in [52][53][54][55].…”

“…Decorrelation, Superadiabaticity [33][34][35][36][37][52][53][54][55] It was discussed earlier that the work q E. v the electric field does on a charged particle is an oscillatory function of time i.e. can be written as a sum of terms proportional to a phase factor exp[iΘ(t)].…”

The 2008 Public Release of the International Multi-tokamak Confinement Profile Database

“…This procedure is reliable for the circular geometry of Tore Supra, and no equilibrium code is required. The Fast Wave power deposition profile has been computed with the codes ALCYON [112] and PION [113], and this is localised inside r/a < 0.2 with more than 90% of the power absorbed by electrons. These hot electron plasmas are characterised by weak electron-ion collisional coupling.…”