A shell model has been formulated for the Hall MHD system, where the Hall term (scaled by the ion skin depth l_i) brings about a new singular perturbation in addition to the resistivity and viscosity effects. The model equations are derived under the constraint to conserve the energy and two helicities in the inertial range. In the limit of l_i → 0, the system reduces to the conventional MHD shell model.

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The ITER Project has been significantly developed in the past years in preparation for its construction. The ITER Negotiators have developed a draft Joint Implementation Agreement (JIA), ready for completion following the nomination of the Project’s Director General (DG). The ITER International Team and Participant Teams have continued technical and organizational preparations. The actual construction will be able to start immediately after the international ITER organization will be established, following signature of the JIA. The Project is now strongly supported by all the participants as well as by the scientific community with the final high-level negotiations, focused on siting and the concluding details of cost sharing, started in December 2003. The EU, with Cadarache, and Japan, with Rokkasho, have both promised large contributions to the project to strongly support their construction site proposals. The extent to which they both wish to host the ITER facility is such that large contributions to a broader collaboration among the Parties are also proposed by them. This covers complementary activities to help accelerate fusion development towards a viable power source, as well as may allow the Participants to reach a conclusion on ITER siting.

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Remarkable progress has been made in the research field of plasma heating and current drive during the past 10 years. Based on an improved understanding of the mechanisms of plasma heating and current drive, various interesting heating and current drive scenarios have been proposed, and many of them have been examined in experiments. A prominent trend is that the established schemes of plasma heating and current drive are now being used as actuators to control the plasma: in order to improve MHD stability, to attain regimes of higher energy confinement time, and to control impurity accumulation. This shift in application, along with the general success of plasma heating and current drive, were made possible by the distinguished progress in RF technology. Chapter 1 of this article reviews the general progress made in the physics of plasma heating and current drive and attempts to give a concept identification of ”controlling the plasma by radio frequency waves”. Chapters 2, 3 and 4, provide comprehensive reviews in the frequency ranges, ECH, LH, and ICRF, giving lights on more specific problems. Chapter 5 addresses the applications of RF heating and current drive to ITER, where readers will find a list of attainments that have survived through critical qualifications.

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Methods of local profile control of electron temperature and current in fusion-oriented devices using electron cyclotron (EC) waves are reviewed. Recent progress in the development of EC heating systems that enable such control is briefly described. The advantageous features of EC wave heating include local and high power density heating properties. Current drive and electron temperature profile control experiments using EC waves performed in order to improve and investigate plasma confinement properties are also discussed.

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Non-inductive current drive (CD) by radio-frquency waves in the lower hybrid range of frequency (LHRF) is one of the most powerful schemes to drive a plasma current and control the current profile of a tokamak plasma externally. This paper reviews recent achievements of CD by LHRF (LHCD) in tokamak experiments with a special emphasis on steady state tokamak operation and profile control in an advanced tokamak.

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Recent progress in plasma control for fusion experiments using ion cyclotron range of frequency (ICRF) heating is described. The paper covers hard ware, plasma experiments and theoretical calculations. Recent developments in high RF power and steady state ICRF heating systems are also described. ICRF heating, current drive and MHD stabilization, and plasma confinement improvement using ICRF power are reported, along with the corresponding progress in theoretical understanding following from developments in simulations.

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Based on the experimental achievements described in the previous chapters, many roles are expected to the RF Heating systems in ITER project. In addition to the main heating to realize D-T burning plasma of fusion energy gain Q ≥ 10, a driver of H-mode transition, start up, steady-state current drive, current profile control, burn control and MHD suppression are required functions. Total heating power of 73 MW will be prepared from the early phase of the ITER operation. The specifications required in the ITER RF heating systems were quite challenging, and included realization of an 1 MW-170 GHz RF source for ECH. Most of them, however, have been satisfied or practically satisfied. The preparations for the construction of the ITER heating systems are completed.

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Alignments of the beam size and position, and the tilt of the propagation axis, have been pointed out to be important in transmission lines for Electron Cyclotron Heating in order to achieve high transmission efficiency. Beam size evolution along the propagation of a Gaussian-like beam, and its beam tilt are analyzed with a quasi-optical moment theory by using measured intensity and phase patterns at a low power level. The Gaussian-like beam is coupled into a corrugated waveguide in the tilted injection. The desired Gaussian content after the coupling is also evaluated in terms of the measured phase as well as the intensity. It is indicated that the direct phase measurements are essential to evaluate the beam size evolution along the propagation, the tilt angle, and the Gaussian content of the beam, which are key issues in the alignment problem.

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New alignment methods of millimeter-wave transmission lines for Electron Cyclotron resonance Heating are proposed and evaluated on a high power level. These methods are based on the measured data of infrared images on the target, which is irradiated by the high power millimeter-waves at several positions. The first and second moments and retrieved phase obtained from these data are used to determine the propagation direction of the millimeter-wave beam along the waveguide axis. It is demonstrated that these methods have sufficient resolution to discriminate 0.1 deg., which is required to restrict the transmission loss below 1% over the 100 GHz range.

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Visualization in data acquisition process is discussed. In order to check the quality of the acquired data, quick plotting of signals is required. Softwares for the data analysis, e.g., plotting applications with GUI and interpreter languages, are compared. Selection of the numerical libraries might be important in determining the optimum language for the analysis.

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A radio frequency (rf) inductive discharge in atmospheric pressure range requires high voltage in the initial startup phase and high power during the steady state sustainment phase. It is, therefore, necessary to inject high rf power into the plasma ensuring the maximum use of the power source, especially where the rf power is limited. In order to inject the maximum possible rf power into the plasma with a moderate rf power source of few kilowatts range, we employ the immittance conversion topology by converting a constant voltage source into a constant current source to generate efficient rf discharge by inductively coupled plasma (ICP) technique at a gas pressure with up to one atmosphere in argon. A novel T-LCL immittance circuit is designed for constant-current high-power operation, which is practically very important in the high-frequency range, to provide high effective rf power to the plasma. The immittance conversion system combines the static induction transistor (SIT)-based radio frequency (rf) high-power inverter circuit and the immittance conversion elements including the rf induction coil. The basic properties of the immittance circuit are studied by numerical analysis and verified the results by experimental measurements with the inductive plasma as a load at a relatively high rf power of about 4 kW. The performances of the immittance circuit are also evaluated and compared with that of the conventional series resonance circuit in high-pressure induction plasma generation. The experimental results reveal that the immittance conversion circuit confirms injecting higher effective rf power into the plasma as much as three times than that of the series resonance circuit under the same operating conditions and same dc supply voltage to the inverter, thereby enhancing the plasma heating efficiency to generate efficient rf inductive discharges.

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