Encouraging progress with Livermore mirror machine

The 2XIIB mirror device at Lawrence Livermore Laboratory has produced plasma temperatures of 10–14 keV, more than four times higher than temperatures reached in an earlier version of the device. Simultaneous with this achievement of reactor‐level temperatures in a dense plasma was a tenfold increase in plasma confinement time, to about five milliseconds. Although these new results are not being taken to mean that magnetic‐mirror confinement has suddenly become the favorite for producing a practical fusion reactor, they do show that the plasma produced in such a device continues to follow classical energy scaling at high temperatures. Confinement time, that is, does increase with energy, indicating that most of the plasma losses are caused by collision between plasma particles rather than by the more serious effects of internal instabilities. Moreover, notes Frederic Coensgen, leader of the California experimental group, the temperature reached was just that predicted two‐and‐one half years ago, and success was achieved within the predicted time and for the predicted cost. Other members of the experimental team are Thomas Simonen, William Cummins, Grant Logan, Arthur Molvik, William Nexsen Jr, Barry Stallard and William Turner.