Tokamaks are devices that use a strong magnetic field to confine a hot plasma that is the shape of a perfect ring / torus.
Tokamaks were developed in the 1950s in the USSR. They were designed to overcome the plasma instabilities inherent in stellarator designs. In the 1970s significant efforts were underway to create operational reactors that would break even with the energy put in equaling the energy put out. Unfortunately containing the heated plasma in a tokamak has proven difficult resulting in damage to the outer walls of various reactors. One of the most successful reactors, the Joint European Torus (JET), that was put into operation in the 1980s is still trying today to reach break even.
Out of the JET project work cooperation between thirty five international partners has led to the multi-billion dollar ITER (“eater”) project currently being built in France. ITER is the largest experimental fusion project ever conceived.
ITER is not the only tokamak being designed and built today. Several private companies have significant financial backing and are pursuit to be the first to produce break even and then better using tokamak designs.
Private companies such as Tokamak Energy are competing with ITER to develop tokamak reactors.