The basic problems of controlled fusion are well known. Briefly they are the following: first, with deuterium or a deuterium‐tritium mixture, to produce a pure low‐density plasma of exceedingly high temperature (several hundred million degrees Kelvin—i.e., several tens of thousands of electron volts); second, to confine this plasma adequately and stably by means of an appropriate magnetic field configuration for a sufficiently long time that an appreciable fraction of the nuclei can undergo fusion; and finally, to capture the energy released and harness it for useful purposes.