October 27, 2006

Melting diamonds, fusion energy advances, lab astrophysics, and more at Philly Plasma Conference

Physicists gather in Philadelphia for world's largest annual plasma conference

Most of the matter we are familiar with in everyday life comes in three states — solid, liquid, or gas. But much more of the matter in the universe exists in a fourth state known as plasma. Plasmas are gaseous collections of electrically charged particles such as electrons and protons. Stars are primarily composed of hot plasmas. On Earth, plasmas are formed in lightning strikes and produce light in fluorescent bulbs. They are used to inscribe patterns in computer chips and other electronics, and they are also at the heart of the most promising nuclear fusion devices that may someday lead to an abundance of cheap, clean, and safe power sources.

Seven international partners, including the U.S., have now committed to the construction of the International Thermonuclear Experimental Reactor (ITER) as the next step toward fusion energy. Many new advances relevant to magnetic confinement in ITER—such as methods to suppress plasma instabilities, control heat loss, diagnose plasma behavior, and enhance heating—have been recently achieved. At the same time, impressive progress in inertially confined fusion plasmas, high-energy-density physics, space and astrophysical plasmas, and basic plasma science has been made.

These highlights and results of many other subjects will be addressed at the 48th Annual Meeting of the American Physical Society's Division of Plasma Physics, to be held October 30-November 3, 2006, in Philadelphia, Pennsylvania. More than 1500 attendees will present 1600 papers covering the latest advances in plasma-based research and technology.

Here are some of the highlights of the meeting:

Philly Science Teachers Visit DPP Meeting and DPP Scientists Take Plasma to Local Schools

During their fall meeting in Philadelphia, the American Physical Society Division of Plasma Physics will be engaging local teachers and students in the study of plasma, the fourth state of matter, through teacher workshops and in-school visits. On "Science Teachers Day," Tuesday, October 31, local teachers will arrive at the Philadelphia Downtown Marriott to receive a special day of training. Over 90 teachers will attend morning and afternoon workshops about plasma and related science. Topics range from space weather, to fluid instabilities, to fusion demonstration activities for the classroom. Scientists will also be visiting local schools. Teams of specialists from Princeton Plasma Physics Laboratory, General Atomics in San Diego, the University of Wisconsin's "Wonder of Physics" program, and the Contemporary Physics Education Group will engage local students with hands-on demonstrations of plasma-related physics.

Diamonds Aren't Forever - Sandia Researchers Use Strong Shock Waves to Melt Diamond

Philadelphia Marriott Downtown - Grand Salon CDE
ZI2.0006, Invited Postdeadline
Friday, November 3, 2006
12:00 AM-12:30 PM

Experiments have been performed at Sandia National Laboratories to measure the melting properties of diamond by studying the speed of sound in diamond subjected to 6 to 10 million times atmospheric pressure. This study represents the highest pressure study of melting ever performed using the sound speed technique. Diamond is one of the materials being considered in the design of fuel capsules for inertial confinement fusion (ICF) experiments at the National Ignition Facility. ICF uses high-powered lasers to vaporize a target capsule containing fusion fuel, creating an implosion that compresses the fuel in the capsule to the temperatures and pressures necessary for fusion. Understanding diamond's shock melting properties is critical to designing capsules and the pulse-shapes that implode them. To reach the high pressures they required, Sandia researchers pounded diamond samples with aluminum/copper plates moving at speeds of up to 54,000 mph (24 km/s). The impact leads to a shock wave traveling at the speed of sound in the diamond. Because sound speed in sensitively dependent on the state of the material, the researchers were able to pinpoint the pressures needed to liquefy the precious stone to between 6 and 7 million atmospheres.

From Zero to a Billion Electron Volts in 3.3 Centimeters

Philadelphia Marriott Downtown - Grand Salon CDE
Thursday, November 2, 2006
10:00 AM-10:30 AM,

Scientists at the Department of Energy's Lawrence Berkeley National Laboratory, in collaboration with researchers at the University of Oxford, have accelerated electron beams to energies exceeding a billion electron volts (1 GeV) in a distance of just 3.3 centimeters. The experiment achieves the highest electron beam energies yet from laser wakefield acceleration, offering the potential of high electron energies over distances much smaller than existing machines. By comparison, the Stanford Linear Accelerator Center (SLAC) boosts electrons to 50 GeV over a distance of two miles (3.2 kilometers). The Berkeley Lab group and their Oxford collaborators achieved 1/50th of SLAC's beam energy in just 1/100,000th of SLAC's length. This is the first time a laser-driven accelerator has reached beam energies typically found in conventional synchrotrons and free-electron lasers. The Berkeley Lab and Oxford researchers were able to increase the acceleration length by lowering the plasma density in order to increase the wake speed, and by using a capillary channel guide carved into sapphire to maintain the collimation of the laser beam. The collaborators are now working to inject energetic beam into an accelerating cavity, and passing beam from one capillary to the next and subsequently to others, until very high energy beams are achieved. The researchers believe they can reach 10 GeV with an acceleration structure less than a meter long.

Bringing Stars and Galaxies Down to Earth: A New Perspective in Astrophysics

Philadelphia Marriott Downtown - Grand Salon CDE
Wednesday, November 1, 2006
10:00 AM-10:30 AM

Laboratory experiments produce scaled-down versions of the powerful jets seen in space, thanks to scientists from both sides of the Atlantic who have developed a new technique to produce in the laboratory, centimeter-sized versions of the powerful jets of plasma observed in young stars, active galaxies and in supernovae explosions. The results provide new insights into the physics of jet formation and open the door to laboratory studies of some of the most remarkable objects in the universe. To create the jets, researchers at Imperial College London used a new technique delivers a millionth-of-a-second pulse of current to an array of micron-sized metallic wires. The experiments, coupled with state of-the-art simulations, show that the sudden release of energy produces inside the hot plasma a magnetic bubble, enveloped by a relatively thin shock-layer that grows into a "magnetic tower." Within the magnetic bubble itself a current-carrying jet appears and the plasma is accelerated to speeds of over half a million miles at temperatures of a million degrees before instabilities in the jet and the "bursting" of the magnetic bubble lead to the break-up of the system. Surprisingly, well-collimated "blobs" of plasma are left behind, forming a relatively narrow channel of energy and mass reminiscent of the clumpy structure observed in many astrophysical jets. Further additions of important physical effects have resulted in the first rotating jets ever produced in the laboratory.

Measuring how High Temperature Plasmas Boil

Philadelphia Marriott Downtown - Grand Salon ABF

Wednesday, November 1, 2006
11:30AM - 12:00PM


Friday, November 3, 2006
9:30AM - 10:00AM

New experimental measurements of plasma turbulence allow for the detailed testing and improvement of models used to predict the performance of future fusion reactors. Hot, magnetically confined plasma is much like a boiling pot of water, and the intensity at which the plasma is boiling often determines how well it is confined. Such a "boiling" plasma is in a state of turbulence, and the chaotic motions of the plasma are called turbulent eddies. These turbulent eddies occur on large and small scales and are associated with the loss, or transport, of particles and energy from the confinement field. Recent collaborative experiments on the DIII-D National Fusion Facility by a team of researchers from the University of California, Los Angeles, University of California, San Diego, University of Wisconsin-Madison, and General Atomics have provided detailed measurements of the turbulence, allowing for the creation of more precise models to predict the performance of future fusion reactors.

The Interactions of Dense Colliding Plasmas with a Background Magnetoplasma

Session GP1
Philadelphia Marriott Downtown - Franklin Hall AB
Tuesday, Oct 31 2006

There are many instances of collisions of ionized material in nature ranging from flares on the sun and astrophysical jets to man-made events such as nuclear detonations in the atmosphere. Although we cannot create these extreme conditions in a laboratory experiment, a detailed study of dense plasmas on a smaller scale can shed light on some of the processes involved when plasmas collide. In an ongoing basic plasma study performed in the LArge Plasma Device (LAPD) the collisions and their aftermath can be studied in great detail. Two Carbon targets immersed in an 18 m long, 60 cm diameter, magnetized Helium plasma, were simultaneously struck by lasers with intensity of approximately 1011 Watts/cm2. The plasma and the laser pulses are highly reproducible, and the experiment is repeated at 1 Hertz. Fully three dimensional data is acquired for up to a million experimental shots. Basic plasma experiments such as this permit highly detailed space-time exploration of phenomena that are related to astrophysical situations. The scaling is never exact but a great deal can be learned in the laboratory, and this can serve as a guide to astronomers and plasma astrophysicists.

Novel Method Developed for Generating Plasma Current in Tokomaks

Philadelphia Marriott Downtown - Grand Salon ABF
Monday, October 30, 2006
10:00 AM-10:30 AM


Philadelphia Marriott Downtown - Franklin Hall AB
Wednesday, November 1, 2006
2:00 PM-5:00 PM

Generating plasma current in tokamaks using Coaxial Helicity Injection (CHI) could lead to smaller, more economical fusion power plants. Researchers at the Princeton Plasma Physics Laboratory have successfully used Coaxial Helicity Injection (CHI) to generate plasma current at the National Spherical Torus Experiment (NSTX) fusion experiment. Until now, most tokamaks have relied on wire coils known as solenoids to start up. But the spherical torus is a form of the tokamak in which the hole through the center of the doughnut-shaped plasma is made very small. While this saves space and allows the externally produced magnetic field to be utilized much more efficiently than in a conventional tokamak, little room is left for a solenoid. Instead the generation of the plasma current by CHI involves a process called magnetic reconnection, which is also involved in the eruption of solar flares on the surface of the Sun. Magnetic reconnection leads to the formation of a magnetic "bubble," in much the same way as blowing a soap bubble stretches a soap film sufficiently so that it detaches from the ring and reconnects to form a bubble. This process of reconnection has been experimentally controlled in NSTX to allow this potentially unstable phenomenon to reorganize the magnetic field lines to form closed, nested magnetic surfaces in the shape of a doughnut carrying a plasma current up to 160,000 Amperes. This is a world record for non-inductive closed-flux current generation, and demonstrates the high current capability of this method. While the CHI method has previously been studied in smaller experiments, such as the Helicity Injected Tokamak (HIT-II) at the University of Washington, the results from the much larger NSTX demonstrate the exciting potential of this method on a scale much closer to that of a fusion reactor.

About APS

The American Physical Society is a non-profit membership organization working to advance and diffuse the knowledge of physics through its outstanding research journals, scientific meetings, and education, outreach, advocacy, and international activities. APS represents over 53,000 members, including physicists in academia, national laboratories, and industry in the United States and throughout the world. Society offices are located in College Park, MD (Headquarters), Ridge, NY, and Washington, D.C.