Tokamak vs. stellerator

The recent cancellation of the National Compact Stellerator Experiment (Notebook, July 16) reminds us that exactly 40 years ago the amazing Russian T-3 tokamak results burst upon the world and blindsided the U.S. stellerator program. The ensuing shutdown of stellerator work at the Princeton Plasma Physics Laboratory, and the rapid adoption of tokamaks at PPPL and other U.S. laboratories, was arguably the most important episode ever in the U.S. magnetic fusion program.

Successively more powerful tokamaks with ever more impressive performance came on line. (The spherical torus discussed in Notebook is a tokamak variant.) Nevertheless, new stellerator projects eventually were funded by the U.S. Department of Energy (DOE) at various fusion labs, with at best lackluster results and usually far worse. Stellerators are more complex magnetic confinement devices than tokamaks, and therefore have always appealed to theoreticians possessing complicated minds and access to supercomputers, but Nature is indifferent to both.

Having learned nothing from decades of tokamak progress and continued stellerator debacles, in the mid-1990s the directorate at PPPL and its counterpart at the DOE reversed the 1968–69 revolution: They decided to shut down the flagship U.S. tokamak (the TFTR) and replace it with a stellerator of unimaginable complexity, the recently aborted NCSX. These foolish decisions have served only to expedite the ongoing demise of the U.S. magnetic fusion program.

(Editor’s note: Jassby was former principal research physicist at PPPL, retiring in 1998.)