First Achievement of Fusion Temperature in a Laboratory (PLT) Princeton Large Torus

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. Scientists at Princeton Plasma Physics Laboratory achieved ion temperatures in excess of 58,000,000 ^oC, the minimum required for a self-sustaining fusion reaction (a condition called ignition), for the first time in 1978. These experiments required a number of advances, most importantly in the development of a powerful new technique for heating a magnetically confined plasma-neutral beam heating. The use of neutral beams to heat plasma dates back to the early 1960s with work performed at the Lawrence Livermore and Oak Ridge national laboratories. Neutral beam heating involves the injection of high currents of energetic neutral atoms into the plasma. The neutral atoms cross the magnetic confinement field and enter the plasma, where they are ionized and confined by the magnetic field. They then heat the plasma through collisions with the plasma ions and electrons. Oak Ridge supplied the neutral beam heating systems used in the Princeton experiments.

Scientific Impact: Neutral beam heating paved the way for major advances in the next generation of plasma confinement devices, which attained ion temperatures suitable for practical fusion energy production and multi-megawatt fusion power levels. It is believed that practical fusion power production will require plasma temperatures in the range of 100,000,000 ^oC to 200,000,000 ^oC.

Social Impact: This advance helped lay the groundwork for promoting fusion as an 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: "Neutral-beam-heating results from the Princeton Large Torus," H. Eubank, R. Goldston, V. Arunasalam, M. Bitter, ..., Phys. Rev. Lett. 43, 270 (1979).

Technical Contact: John Willis, Research Division, 301-903-4095

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

SC-Funding Office: Office of Fusion Energy Sciences