General Physics Seminar 11 December 2003


Rope-Dancing in a Tokamak:
An integral ECCD feedback control system for suppression of (neoclassical) tearing modes

Egbert Westerhof
FOM Instituut voor Plasmafysica Rijnhuizen,
P.O. Box 1207, 3430 BE Nieuwegein, The Netherlands


In spite of the possible catastrophic consequences of the loss of stability, tokamak reactors and ITER will typically operate close to the stability boundaries. This will put high demands on plasma control systems. Because of its unrivaled localisation, ECRH/ECCD is ideally suited as actuator for plasma stability control. An example is the control of neoclassical tearing modes (NTM) by ECCD, which requires the balancing act of a rope-dancer in order to position and keep localised the ECCD inside the magnetic islands created by the mode.

We have recently proposed a novel scenario for NTM control that solves this balancing act in a straightforward and simple manner. The challenges and possible pitfalls associated with this scheme of "same sightline ECE" will be discussed.