Plasma science (the study of ionized gases) is critical to the development of fusion energy (involving the fusion of nuclei), which could be an abundant energy source in the future. A key to developing a fusion energy source is the formation and maintenance of the complex magnetic fields that confine the plasma. In a tokamak device, a toroidal current in the plasma is a critical component of the magnetic field. In the 1970s, physicists proposed that the pressure gradient in fusion plasma gives rise to a powerful "bootstrap current." This prediction was confirmed in the 1980s, and the bootstrap current was demonstrated at fusion-relevant temperatures in excess of 100,000,000 °C at Princeton Plasma Physics Laboratory. In addition, with Office of Science support, theorists at the Massachusetts Institute of Technology predicted that radio-frequency electromagnetic waves could produce a net flow of electrons in a tokamak—similar to surfers being moved by a wave—thereby generating a strong current efficiently enough to be useful in a fusion power plant. This research was verified by experiments in Japan and the United States. For this work, researchers from both countries, including scientists from MIT and PPPL, won the American Physical Society Excellence in Plasma Physics Research Award in 1984.

Scientific Impact: This work extended earlier pioneering research on the natural symmetry between thermodynamic forces and the particle fluxes they support, and on wave-particle interactions. It is now possible to maintain and control the magnetic field profile in an advanced tokamak configuration with a combination of bootstrap and radio-frequency wave drive currents.

Social Impact: These advances will help promote the availability of fusion as an inexhaustible, safe, and environmentally attractive energy source. In addition to the general public, beneficiaries may include industries that use plasma science and technology, including makers of semiconductors and space propulsion systems.

Reference: "Theory of Current Drive in Plasmas," Nathaniel J. Fisch, Rev. Mod. Phys. 59, 175 (1987)

"Bootstrap Current in TFTR," M. C. Zarnstorff, M. G. Bell, M. Bitter, ..., Phys. Rev. Lett. 60, 1306 (1988)

URL: http://www.pppl.gov/projects/pages/tftr_achievements.html

Technical Contact: Curt Bolton, Research Division, 301-903-4914

Press Contact: Jeff Sherwood, DOE Office of Public Affairs, 202-586-5806

SC-Funding Office: Office of Fusion Energy Sciences