Alternatives to tokamaks: a faster-better-cheaper route to fusion energy?

The use of thermonuclear fusion as a source for energy generation has been a goal of plasma physics for more than six decades. Its advantages are many: easy access to fuel and virtually unlimited supply; no production of greenhouse gases; and little radioactive waste produced. But heating fuel to the high temperature necessary for fusion-at least 100 million degrees Celsius-and containing it at that level has proved to be a difficult challenge. The ring-shaped magnetic confinement of tokamaks, which emerged in the 1960s, was quickly identified as the most promising approach and remains so today although a practical commercial reactor remains decades away. While tokamaks have rightly won most fusion research funding, other approaches have also been pursued at a lower level. Some, such as inertial confinement fusion, have emerged from nuclear weapons programs and others from academic efforts. A few have been spun out into start-up companies funded by venture capital and wealthy individuals. Although alternative approaches are less well studied, their proponents argue that they could provide a smaller, cheaper, and faster route to fusion energy production. This article will survey some of the current efforts and where they stand. This article is part of a discussion meeting issue 'Fusion energy using tokamaks: can development be accelerated?'.