Helicon Plasma

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 and attractive energy source in the future. An important parameter in plasma science is the current density profile, which is fundamental to the equilibrium, stability, and transport of particles and heat in plasma. Fusion Physics & Technology, Inc., a small business, used DOE funding to develop a technique for measuring the internal magnetic field in fusion plasmas, thus making it possible to determine the current distribution. This technique uses a beam of neutral atoms that propagates across the magnetic field in fusion plasma. The resulting electric field causes a wavelength splitting and linear polarization of the radiation emitted by the beam atoms that are excited by collisions with background gas. The direction of polarization indicates the magnetic field pitch angle, from which scientists can compute the plasma current density profile. This measurement technique was first implemented at the Princeton Plasma Physics Laboratory. The principal investigator, Fred Levinton, received the American Physics Society Award for Excellence in Plasma Physics Research in 1997 for this pioneering work.

Scientific Impact: Results of measurements made with this technique have made important contributions to understanding of the physics of plasmas, especially heat and particle transport, and have provided a basis for comparison with theory. The technique has become widely accepted, and similar instruments are operating on many fusion experiments around the world.

Social Impact: This innovation 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: "Magnetic Field Pitch-Angle Measurements in the PBX.M Tokamak Using the Motional Stark Effect," F. M. Levinton, R. J. Fonck, G. M. Gammel, R. Kaita, ..., Phys. Rev. Lett. 63, 2060 (1989)

URL: http://w3.pppl.gov/tftr/overview/mse.html

Technical Contact: Darlene Markevich, Research Division, 301-903-4920

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

SC-Funding Office: Office of Fusion Energy Sciences