Progress in Design and R and D for in-Vessel Coils for ITER, DIII-D, and JET

Full text: Much progress has been made in the R and D and design of in-vessel coil systems for DIII-D, ITER, and JET as the result of a coordinated effort to develop acceptable performance, mechanical design, materials, analysis and manufacturing techniques for Edge Localized Mode (ELM) control. This paper presents the status of these design and R and D efforts at PPPL. First wall and divertor erosion and damage caused by ELMs is a major hurdle on the route towards high performance, long pulse operation of ITER and achieving magnetic fusion in a reactor scale machine. Presently the most promising method of mitigating, or even completely suppressing ELMs is to apply resonant magnetic field perturbations (RMP) in the plasma edge. This technique to suppress ELMs was discovered on DIII-D, and experimentation continues on DIII-D and several other machines. Because of the importance of mitigating ELMs, a set of RMP coils is being designed for ITER, based on empirical criteria developed on DIII-D. A new set of center-post mounted coils, scheduled for installation in DIII-D beginning in 2010, has been designed to extend their physics studies A design study for JET has demonstrated the feasibility of a system of in-vessel RMP coils, including installation by remote handling, that would satisfy ELM suppression criteria for all of JET's ITER-relevant scenarios. Experiments with these upgrades will provide additional information towards the understanding of ELM control by RMP, and extend the dataset for extrapolation towards ITER-like plasmas. There is some commonality of design aspects in the three designs, such as the need for high temperature insulation, high reliability due to their in-vessel locations, and the need for vacuum jacketing Prototypes of the DIII-D coils are being fabricated. This effort includes the development of low-distortion welding techniques for the vacuum jackets and qualification of high-temperature insulation, also required for JET. There are also differences in operational characteristics of the three tokamaks which have dictated significantly different design solutions. The in-vessel environments of the three machines leads to differences in material selection and in the need for remote handling. The primary design drivers for all 3 devices will be discussed in detail, as well as proposed design solutions. (author)