C16. Commission on Plasma Physics

C16 Report: Plasma Science Highlights

Fusion:

In the past one year there has been a steady progress in the evolution and structure of the ITER program. Thanks to the concerted efforts of the seven members the final decision on the choice of site seems imminent. The expanded membership has also strengthened the scientific and technical resources of the program and will help speed up the construction and commissioning phase once the site selection process is over. The Indian initiative to join the ITER program has received a very favorable response. An expert team from the European Commission plans to visit India in mid-November, 2004 for scientific/technical evaluation and discussions with concerned scientific officials.

Plasma based particle acceleration:

There have been some significant recent developments in the field of plasma wakefield acceleration. Experiments carried out in France, England and the U.S.A. provide the first demonstration that a beam of electrons can be accelerated in a wakefield to a single energy. Moreover, these beams are of high quality (having a small angular divergence) and significant charge (about 10 9 electrons). The experiments reveal a new physical regime, in which electrons are ‘self-injected’ in a narrow region of space and surf as a single group, all reaching the same energy. When 10–30 terawatts of laser power, in pulses 30–55 femtoseconds long, is focused into an ionized jet of gas roughly 2 mm long and with a particle density of 2 ´ 10 19 cm -3 ; a nearly monoenergetic distribution of electrons is observed, with instrument-limited energy spreads of 2–24% at roughly 80–170 MeV. With up to a few times 10 9 electrons per beam, the energy densities in these experiments are a hundred to a thousand times higher than has previously been achieved.

The angular spread of the beams is also about ten times tighter than before — comparable

to the best of the beams produced by radio-frequency systems. Moreover, the pulse lengths of the beams are about 10 femtoseconds, making them attractive as potential radiation sources for ultra fast time-resolved studies in biology and physics.

Industrial plasma applications:

Over the past few decades activities in the area of weakly ionized gases or "cold" plasmas have been driven to a very large extent by industrial interests. Following the explosive growth of plasma processing for microelectronics in the 1980's – plasmas are being used more and more in applications for materials processing, welding/cutting, pollution control, and many other areas. These "plasma engineering" activities are often found in the applied science departments at universities – in the electrical, mechanical, aerospace, or chemical engineering or even in biology departments (e.g. plasma sterilization, plasma "needle",etc). These wide ranging applications with their focus on process rather than on plasma still demand considerable plasma physics expertise. The plasma physics conferences traditionally supported by IUPAP – ICPIG and ICPP– provide essential forums for applied physicists and engineers working in these diverse applications to meet with each other and with other plasma physicists in areas less driven by applications.

Not surprisingly, there are many common research issues in spite of the apparent diversity. A few examples of on going, cross-disciplinary areas of research are:

• Non-thermal plasmas (cold background gas) generated in atmospheric pressure gases reduce the need for large vacuum installations but are notoriously difficult to control. Generation and maintenance or "control of non-thermal plasmas at atmospheric pressure" is a huge topical area with many fundamental issues still to be resolved.
• New applications and complex physical phenomena are to be found at the interface of plasma physics and fluid dynamics. These two large communities are just now starting to join forces and to unravel some of the complexities resulting from the coupling of plasmas and rapidly flowing gases. Specific examples include plasma-aided or enhanced combustion, plasma control of flows etc.
• Each advance in electronics or materials offers new possibilities for plasma-based applications and opens new research areas. For example, the ability to reliably fabricate small scale features, the availability of miniaturized electron drivers, and considerable tuning of the plasma have led to today's commercially-available plasma display panel technology.
• More and more complex plasma chemistries are being used in processes, and the plasma chemistry and plasma-surface interactions have become active areas of basic and applied research.