How Nuclear Fusion Reactors Work

By: Patrick J. Kiger & Craig C. Freudenrich

Fusion Reactors: Magnetic Confinement

Plasma toroid
Courtesy ITER

There are two ways to achieve the temperatures and pressures necessary for hydrogen fusion to take place:

  • Magnetic confinement uses magnetic and electric fields to heat and squeeze the hydrogen plasma. The ITER project in France is using this method.
  • Inertial confinement uses laser beams or ion beams to squeeze and heat the hydrogen plasma. Scientists are studying this experimental approach at the National Ignition Facility of Lawrence Livermore Laboratory in the United States.

Let's look at magnetic confinement first. Here's how it would work:


Microwaves, electricity and neutral particle beams from accelerators heat a stream of hydrogen gas. This heating turns the gas into plasma. This plasma gets squeezed by super-conducting magnets, thereby allowing fusion to occur. The most efficient shape for the magnetically confined plasma is a donut shape (toroid).

A reactor of this shape is called a tokamak. The ITER tokamak will be a self-contained reactor whose parts are in various cassettes. These cassettes can be easily inserted and removed without having to tear down the entire reactor for maintenance. The tokamak will have a plasma toroid with a 2-meter inner radius and a 6.2-meter outer radius.

Let's take a closer look at the ITER fusion reactor to see how magnetic confinement works.