Tandem‐mirror machines promise better efficiency

A major problem with magnetic‐mirror devices for plasma confinement has always been the leakage of particles out of the ends of the machine. An experiment now under construction at Lawrence Livermore Laboratory, known as the Tandem Mirror Experiment (TMX), proposes to turn this failing neatly to advantage by employing two mirror‐pairs, one at each end of a long straight solenoid. Each pair of mirrors confines positive ions by minimum‐B magnetic‐field wells, and the excess positive charge that develops in these “end cells” confines ions within the solenoid. In other words, the two mirror pairs act as plugs for the ends of the solenoid. Calculations for a reactor based on this concept predict that, under appropriate neutral injection conditions, a plasma of a density and temperature sufficient for controlled fusion will build up in the solenoid. The purpose of the TMX experiment is to test the principles of the concept. Other tandem‐mirror experiments are planned or already under construction at Novosibirsk in the Soviet Union, at the University of Tsukuba in Japan, and at the University of Wisconsin at Madison.

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