Electron-cyclotron heating of toroidal plasma with emphasis on results from the ELMO Bumpy Torus (EBT)

Microwave heating at the electron-cyclotron frequency has been effectively employed to heat plasmas confined in open and closed magnetic confinement geometry where the applied heating frequency was near or above the plasma frequency. The earliest experimental investigations demonstrated the effectiveness of plasma electron-cyclotron heating (ECH) and later theoretical work validated these observations. In this review, we briefly consider some of the more relevant ECH propagation processes and heating mechanisms. Results are presented from some of the more recent toroidal ECH experiments, including tokamaks, but principally from the ELMO Bumpy Torus (EBT). In the last section, we discuss the technological considerations so important to successful applications of ECH to plasma experiments

Gyrotron: an ECH system component

The gyrotron, or electron-cyclotron maser, in the form of a gyromonotron, is being developed as a source of millimeter wave energy for fusion plasma heating. The characteristics of this high power, high efficiency electron tube are described in terms of the requirements for the beam power supply system, the mechanical support system, the cooling system, the focusing and tuning magnets, and the waveguide system. Requirements of power level and transmission efficiency dictate the use of oversize waveguide. The implications, both to the user and to the interaction mechanisms in the gyrotron, of the use of oversize waveguide are treated. The effects of variations of various operating parameters upon the gyrotron's power output and stability are also discussed. Data from gyrotron development and system operation are used where appropriate