Magnetic Confinement Experiment: I: Tokamaks
Author: R.J. Goldston
Reports were presented at this conference of important advances in all the key areas of experimental tokamak physics: Core Plasma Physics, Divertor and Edge Physics, Heating and Current Drive, and Tokamak Concept Optimization. In the area of Core Plasma Physics, the biggest news was certainly the production of 9.2 MW of fusion power in the Tokamak Fusion Test Reactor, and the observation of unexpectedly favorable performance in DT plasmas. There were also very important advances in the performance of ELM-free H- (and VH-) mode plasmas and in quasi-steady-state ELM'y operation in JT-60U, JET, and DIII-D. In all three devices ELM-free H-modes achieved nTt's `~2.5Y greater than ELM'ing H-modes, but had not been sustained in quasi-steady-state. Important progress has been made on the understanding of the physical mechanism of the H-mode in DIII-D, and on the operating range in density for the H-mode in Compass and other devices. In the area of Divertor and Edge Physics the major new advance is that pumped divertors are now nearly routine "tools of the trade," used for helium pumping, density control, and impurity control. Experiments on DIII-D demonstrated clear control of density, as well as helium pumping quite adequate for a reactor - in ELM'ing mode plasmas. The ASDEX-Upgrade team reported results in which feedback control of both deuterium and neon puffing allowed operation in a so-called "Completely Detached H-mode (CDH)." In this mode even energy dumps from ELMs did not burn through to the divertor plate. The first results from vertical-plate divertors in C-Mod and JET are very promising. The C-Mod team has also shown successful ICRH heating in an all-molybdenum machine. In the area of Heating and Current Drive, there were many advances, but perhaps the clearest theme was the multiplicity of applications that have been found for ion-cyclotron-range-of-frequency- RF power. Alfven wave current drive has been demonstrated on Phaedrus-T; second harmonic tritium heating has been explored on TFTR, as has mode-conversion current drive. Ion Bernstein waves have been used to create a core transport barrier in PBX-M, and progress has been made on fast wave current drive on both Tore Supra and DIII-D. At higher frequencies, lower-hybrid current drive is now becoming a reliable and well-understood tool for current profile control in JT-60U and JET.