Black Holes, Fusion, and Nanotubes Featured at DPP Meeting
The APS Division of Plasma Physics held its 51st annual meeting in Atlanta, Georgia in early November. The meeting brought together over 1,500 scientists specializing in plasma physics to share the latest research in the field. In addition to the science program, the meeting invited local school groups and the general public to come in and meet the physicists to discover more about the importance of plasma physics.
Bruno Coppi from MIT presented a solution to the mystery of anomalous X-ray emissions emanating from the vicinity of young black holes. These powerful signals, usually observed coming from large newly-formed black holes, shoot out into space as part of powerful jets perpendicular to their accretion disks. Coppi showed, using information gathered from confined laboratory plasmas, that eddies in the spiraling plasma around the inner edges of a black hole’s accretion disk can create oscillating magnetic fields. These fields excite the spinning plasma, causing the repeated emissions of high energy X-rays visible from Earth.
The National Ignition Facility
The recently christened National Ignition Facility at Lawrence Livermore National Laboratory is poised to dramatically advance fusion research. Technicians there will focus nearly two hundred of the world’s most powerful lasers on a small target of deuterium, creating conditions for the isotope to ignite, producing more energy through fusion than was used. The design of the deuterium target’s container, known as a hohlraum, is critical for fusion to take place. Numerous presenters evaluated and proposed possible refinements to the hohlraums used at the NIF. Nathan Meezan of Lawrence Livermore gave an overview of ongoing experiments to get the most efficient energy transfer from the incident lasers. Dustin Froula from Lawrence Livermore presented his analysis of the gas- filled hohlraums at the OMEGA laser in Rochester NY to predict how the NIF’s laser will behave inside the highly energized plasma of a fusion reaction. Similarly, Otto Landen, also at Lawrence Livermore, reported on a series of test shots at the OMEGA laser of differently configured hohlraums designed to fine-tune their effectiveness.
Lasers are only one method being investigated to generate fusion power. Tokamak reactors, which enclose rapidly spinning high energy plasma inside toroidal magnetic fields, have been the focus of research since the 1950s. T.C. Luce of General Atomics presented a comprehensive overview of what such a theoretical tokamak power plant might look like. In doing so, he outlined many of the recent advances in tokamak technology that have improved their stability, ability to contain the pressure, and current drive. He showed how one of the biggest looming problems with up-scaling them for industrial power production is the containment of their intense heat and particle fluxes generated by the spinning plasma.
Plasmas have numerous practical applications outside of power generation, often in unexpected ways. Single-walled carbon nanotubes hold tremendous promise for future technologies because of their unique structural and electrical properties. One of the most common ways to produce them is the arc discharge method, where the nanotubes are produced out of the arcing plasma during a high powered electrical discharge between two carbon rods immersed in an inert gas. Michael Keidar of George Washington University described new ways being investigated to use electrical and magnetic fields to manipulate the length of carbon nanotubes using the arc discharge method.