Plasma Meeting Features Research on High Pressures, Fusion Reactors, and Etching
From the DPP Meeting
Coming from the National Ignition Facility at Lawrence Livermore National Laboratory is news that a team compressed a diamond sample to 50 megabars of pressure, a new record. Raymond Smith of LLNL described his team’s experiment using a pulsed 750 kilojoule laser to gradually compress a small diamond sample to 50 million times Earth’s atmospheric pressure. Studying the behavior of diamond at such high pressure is a relatively new field. Traditional quasi-static compression methods peaked at only about three megabars, while this relatively new “ramp-compression” technique can achieve much higher pressures. This kind of crushing pressure is thought to be found in the cores of some “super-earths” discovered orbiting distant stars, and the researchers said that this technique can offer clues to their formation and inner structure.
The effort to build a viable fusion energy source continues as scientists work to improve tokomak reactors. Physicists from General Atomics presented at several sessions different new experimental techniques to prevent rare but potentially dangerous “beams of very energetic ‘runaway’ electrons” when a major fault happens inside a reactor. Another team, led by Rajesh Maingi of Oak Ridge National Laboratory, found that lining the walls of a fusion reactor increases its efficiency and is more effective at containing hot ionized plasma. Sometimes when the heated plasma inside the reactor interacts with the reactor walls, it knocks off impurities as a kind of “ash” into the plasma stream, reducing its efficiency. Physicists at MIT are using a laser to introduce impurities into one of their reactor’s plasma stream so they can chart their effects and model how they behave.
Plasmas also play a role in building cutting-edge microchips. Richard Gottscho from Lam Research described his team’s latest work improving methods to fabricate transistors and other micro-electronic devices using plasma etching. For years plasmas have been used to “fill in” imperfections in micro-wires left over from the lithographic fabrication process. Gottscho and his team are working to develop a process to etch off a single layer of atoms from the nanowires to better shape them.