fusion Theory & Computation

TORIC Full wave RF mode conversion

Heating and Current Drive

An improved understanding of the propagation and absorption of radio frequency (RF) waves is an important aspect of controlled fusion research as these waves can be used for plasma heating to fusion temperatures, driving currents to make non-inductive operation of tokamaks feasible, and to generate localized plasma flows and currents for profile control in tokamaks.

The PSFC theory group has conducted extensive computational and theoretical studies of RF heating, mode conversion, and current drive in the ion cyclotron range of frequencies (ICRF) and in the electron cyclotron range of frequencies (ECRF). We have conducted seminal studies of minority heating in tokamaks and full wave propagation in the lower hybrid range of frequencies (LHRF). These studies include detailed investigations of LH current drive, comparing 2-D numerical solutions of the Fokker-Planck equation with results from the adjoint formalism.

This work will directly benefit upcoming LH current drive experiments on the Alcator C-Mod tokamak. Our research on ECRF waves is motivated by the need to drive current for profile control and for stabilizing instabilities, like the neoclassical tearing mode, in spherical tokamaks (ST). Since the plasmas in STs are overdense to conventional ECRF waves, electron Bernstein waves (EBW) offer an attractive possibility in the EC range of frequencies. These studies will benefit future experiments on NSTX and MAST.

Examples of recent accomplishments:
* Implemented the full wave ICRF solver TORIC on our parallel computing cluster
* Used TORIC to model ICRF mode conversion and a synthetic PCI diagnostic
* Performed the first full wave simulations of lower hybrid waves in a tokamak
* Demonstrated feasibility of electron Bernstein wave heating and current drive in STs
* Developed a new kinetic code to study synergistic enhancement of RF current drive

Representative current research topics:
* ICRF mode conversion flow drive and current drive triggers of internal barriers
* Lower hybrid propagation, current drive and Fokker-Planck studies
* Synergistic current drive by combined lower hybrid and ion cyclotron waves
* Parametric excitation coupling of high harmonic fast and electron Bernstein waves
* Electron Bernstein wave propagation, damping, and current drive

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