Nontokamak

Nontokamak refers to magnetic confinement fusion devices that do not rely on the tokamak geometry as their primary confinement method. Unlike tokamaks, which use a large toroidal plasma current to generate part of the confining magnetic field and can experience disruptions, nontokamak approaches typically aim to confine hot plasma using externally generated magnetic fields or self-organizing current structures without the same disruption risks.

Major non-tokamak approaches include stellarators, reversed-field pinches, spheromaks, field-reversed configurations, and magnetic mirrors. Stellarators confine plasma with carefully shaped external coils to produce a three-dimensional magnetic field that is inherently steady-state and does not require a large plasma current. Spheromaks and field-reversed configurations are compact toroids that form and sustain magnetic fields with more self-contained current systems. Magnetic mirror systems use open magnetic field lines to reflect charged particles and can be configured as linear or end-plugged devices. Some research also explores hybrid concepts and quasi-symmetric coil designs that blend features of different approaches.

Advantages of non-tokamak designs include potential for steady-state operation (especially in stellarators) and reduced risk of disruption. Challenges include complex coil geometries and engineering demands, lower confinement quality in some configurations, and the need for sustained net energy gain demonstrations. Progress varies by device type, with notable successes in achieving long confinement times and steady-state operation in stellarator experiments such as Wendelstein 7-X, and ongoing investigations in other programs worldwide.

In summary, nontokamak research encompasses a range of confinement concepts that seek reliable, disruption-resistant paths toward fusion energy, complementing tokamak efforts and expanding the landscape of magnetic confinement science.