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Home / Publications / Journals / Fusion Science and Technology / Volume 47 / Number 3 / Pages 345-354

Advanced Control Techniques and High Performance Discharges on DIII-D

A. G. Kellman for the DIII-D Team

Fusion Science and Technology / Volume 47 / Number 3 / April 2005 / Pages 345-354

Technical Paper / Fusion Energy - Experimental Devices and Advanced Designs

The advancement of plasma control techniques has enabled significant progress to be made toward the scientific understanding and realization of Advanced Tokamak operation on DIII-D. The Advanced Tokamak features fully noninductive current drive, operation at high plasma pressure and high energy confinement time. These features require efficient current drive systems, simultaneous control of plasma current and pressure profiles, and active feedback control of plasma instabilities. A number of key systems on DIII-D have been developed to provide this control capability. A versatile electron cyclotron heating and current drive system is routinely providing in excess of 2 MW of power for pulse lengths from 2 to 5 s. This system has been used to provide offaxis current drive, direct electron heating and pressure profile modification, and stabilization of the Neoclassical Tearing Mode instability. A combination of control of magnetic error fields, neutral beam induced plasma rotation, and active feedback stabilization using both external and internal nonaxisymmetric coil systems has been used to stabilize the Resistive Wall Mode at high values of plasma pressure. Control of the ELM instability has recently been demonstrated using the newly installed internal coil system. The higher speed and expanded realtime diagnostic capability of our recently upgraded plasma control system permits these various control techniques to be simultaneously integrated to achieve our high performance discharges. This has resulted in fully noninductively driven plasmas with N = 3.5 and T = 3.6% sustained for up to 1 s. Upgrades and facility modifications to further enhance our control and scientific capabilities including rotation of a neutral beamline, expanded EC system power, and installation of a new lower divertor are discussed.

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