Speaker
Dr
Robert Pinsker
(General Atomics)
Description
Modeling shows that fast waves at very high ion cyclotron harmonics (also called “whistlers” or “helicons”) can drive current efficiently in the mid-radius region of a high beta tokamak plasma, as is required to sustain steady-state high performance discharges in a DEMO-like configuration. DIII-D has developed discharges with high electron beta and high electron temperature so that full first-pass damping of the waves is expected to take place off-axis. We show that in a specific existing high-beta DIII-D target discharge, 0.5 GHz fast waves at launched n_|| ~ 3–4 would drive a noninductive current of 60 kA/MW at ρ=0.55, where the electron density is ~5x10^19 m^-3 and the electron temperature is ~3 keV. With complete first-pass absorption, loss processes (mode conversion, far-field sheath formation, etc.) associated with weak single-pass damping are minimized. The calculated current drive efficiency is 2 to 4 times higher than that of off-axis neutral beams or electron cyclotron current drive using the present DIII–D systems. Strong, radially localized absorption on electrons can be obtained only for local values of βe exceeding 1.8%. At lower values, the waves propagate to smaller minor radius before being absorbed. Varying the launched value of n_|| shows that the driven current hardly changes in either magnitude or in radial location in the range of 2.8
| Country or International Organisation | USA |
|---|---|
| Paper Number | TH/P2-38 |
Primary author
Dr
Robert Pinsker
(General Atomics)
Co-authors
Dr
Charles Moeller
(General Atomics)
Prof.
Miklos Porkolab
(MIT)
Dr
Orso Meneghini
(Oak Ridge Associated Universities)
Dr
Ron Prater
(General Atomics)
Prof.
Victor Vdovin
(Tokamak Physics Institute NRC Kurchatov Institute)
