Inside Walter Gekelman's warehouse-sized laboratory in Westwood Village, enough electricity to power a thousand homes pours into a row of 68 magnet rings, each one weighing half a ton.
A steady pulse of brilliant red light flashes from inside the cylindrical machine--as tall as a bus and twice as long. With each pulse, a thimble's worth of neon gas seeps into the near-vacuum inside the machine and directly into the path of a 500,000-watt electron beam. As temperatures shoot to a quarter-million degrees, a curious form of matter known as a plasma is created. It lasts only a few thousandths of a second. Any longer and the 80-ton Large Plasma Device would melt.
Plasma makes up well more than 99% of the "stuff" of the observable universe. Thin wisps of plasma occupy the vast near-vacuum of interstellar space. Plasma is the main ingredient of stars--dense as iron and 5 million degrees at the sun's core. Lightning, licks of fire and fluorescent light bulbs are earthly examples of tiny amounts of plasma. Yet this universally common form of matter is a rarity on our relatively cool, dense planet--perhaps why the study of plasma is one of the youngest fields of physics.
Atoms as we normally know them each consist of a central nucleus orbited by charged electrons. This relationship is faithfully maintained even as materials shift from solid to liquid to gas. A plasma, by contrast, is ionized--its atoms "stripped" of electrons.
"I always ask my students what happens if we keep making steam hotter and hotter?" said Gekelman, a UCLA professor. As a material is heated, its atoms vibrate more and more intensely. At extreme temperatures, orbiting electrons are literally shaken loose from their nuclei. "It's at this point that you have a plasma," he said.
First described by 19th century physicist Sir William Crookes, plasma wasn't named until American chemist Irving Langmuir coined the term in 1929. During the 1950s, as physicists worked on testing hydrogen bombs, they realized that the extremely hot plasmas formed by the nuclear explosions could be used to generate energy. Born classified, research on nuclear fusion and plasmas remained secret until 1958.
Today, researchers like Gekelman study the fundamental properties of how waves of energy flow across and through plasma. Among the behaviors the Large Plasma Device is designed to study is the ability of a plasma to, in effect, store a memory of energetic disturbances that pass through it.
