Tokamak Edge Stability

Like the surface of the sun, the edge of tokamak plasmas are susceptible to bursty instabilities that must be controlled to interface the hot plasma to a material wall.

High performance tokamaks can be unstable to the “Edge Localized Mode”, a phenomenon that results in the rapid ejection of plasma towards the material wall (see image). A central goal of the worldwide fusion research program is to find ways to control this instability, while preserving the high fusion performance needed to create an economical tokamak fusion reactor. Research in this area is focused on finding solutions to control the ELM.

Tokamak Edge Stability

Research into the edge stability of tokamak plasmas focuses on ways to control the ELM instability.

One technique Columbia researchers actively develop is the use of purpose-build electromagnets that apply small corrugations to the plasma boundary, with several examples pictured above. This technique is foreseen to be a primary method of controlling the ELM in the ITER fusion reactor, currently under construction in France.

Topics of active research include comparing results obtained on tokamak facilities in the United States with companion facilities overseas. Comparing results from different facilities allows understanding of the common features of this control technique. Active research is also taking place in designing new types of electromagnet geometries to better achieve ELM control in current and future facilities.

Columbia researchers are also actively developing plasma scenarios naturally free from the ELM instability. These scenarios are described here: Reactor Scenarios.

DIII-D Tokamak

Edge stability research on the DIII-D tokamak focuses on the use of small electromagnets to control the ELM, and the exploration of novel plasma scenarios naturally stable to the ELM.

International Tokamaks

Work at international research facilities enables targeted comparisons of ELM control phenomena under a wide range of plasma conditions.

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