Newsgroups: sci.physics.plasma
From: moderator
Subject: PS&T Dialogue

A COMMUNITY-WIDE DIALOGUE IN PLASMA SCIENCE & TECHNOLOGY

Mesoscale Processes in a Multi-scale World

Plasma science is as rich as any other state of matter in terms
of distinct processes and interactions and they encompass distinguishable
scales ranging from the atomic to the galactic. Opportunities in plasma
science and technology reflect this breadth in phenomena and scales.
The problem of understanding linkages in multi-scale processes is
a frontier problem of modern science. Mesoscale physics has to do with
understanding how the different scales interact. "Meso" denotes "middle"
or "intermediate" and here mesoscale is defined by context and not by any
particular scale length. Mesoscopic or mesoscale processes are
encountered from condensed matter physics to space plasmas, from 10-7m to
10+7m. The relationship of microscopic to macroscopic phenomena has long
been a central theme of statistical mechanics and other fields. However,
the natural emergence of distinct mesoscale processes and structures is a
relatively new development.

Plasma: An Ideal System for Mesoscale Research

Collisionless plasma is a unique statistical system where it is
possible to make measurements with resolution ranging from less than the
smallest relevant spatial scale, the Debye length, to the full ensemble
scale. New and emerging technologies enable the formulation of
qualitatively and quantitatively advanced kinds of experiments.
For example, new plasma sources can couple to electromagnetic fields
ranging from near-zero to x-ray frequencies. In fact, the promising
performance of plasma-loaded microwave devices is generating considerable
interest in the new field of plasma microwave electronics which is rich
with new physics associated with beam/plasma/wave interactions.
Short-pulse and high-power lasers enable new diagnostics of both
single-particle and collective effects that are both penetrating and
nearly ideal in that they produce only a slight perturbation. New
microfabrication techniques make possible sophisticated particle and
field probes with spatial resolution better than a Debye length in
laboratory plasmas. Indeed, certain plasma systems provide the simplist
possible physical systems where both the computational modeling and
relevant physical measurements are possible at all scale lengths; micro-,
meso-, to macroscale. Mesoscale phenomena are critical to the
development of a more complete and coherent picture of plasma physics and,
more generally, the nonequilibrium statistical mechanics of classical
systems dominated by collective interactions.

Plasma Physics and the Technological Infrastructure

Plasma science and the understanding of mesoscale phenomena have
an important contribution to make to any country's technical infrastructure.
The potential applications of plasma science are as rich and diverse as for
any other state of matter although most applications known to date
have emerged only within the past decade. One example of these potential
applications is advanced microchip manufacturing. Plasma processing is
becoming an increasingly important microelectronic technology and electron
and ion beam projection lithography, where charged particle beams can
produce chip features on nanometer scale, may be a technology of choice
for the future. Applications of plasma science are emerging in many areas
such as advanced microwave devices, vacuum microelectronics, relativistic
electronics,materials processing, pure diamond film deposition, flat-panel
displays, pulsed power devices, ceramic production, space environment and
impacts on technological systems such as communications spacecraft or
ground-based power grids, production of high-temperature superconducting
film, manufacture of fullerenes, metal extraction and processing, plasma
thrusters, and toxic waste treatment.
Because it is so highly interdisciplinary, students trained in
plasma science have a broad range of technical competence. This includes,
among others, the fields of optics, materials science, electrical power,
electronics, magnetohydrodynamics, high voltage, pulsed power, ultra-high
vacuum, computer applications, spectroscopy, atomic physics, nonlinear
dynamics, lasers, microwave generation, and particle detection. It is
the new and interdisciplinary nature of plasma science which has made
it difficult to integrate it into existing academic and governmental
structures. Within the U.S. National Science Foundation (NSF), for
example, the fourth state of matter does not appear in the telephone
directory. Further, investments in plasma science and technology are
less than about 2% of investments made for research involving the other
three states of matter although it has some presence in about half of
all NSF divisions.

New Experimental Possibilities

New experiments are now possible which address the fundamental
structure of plasmas. High-performance plasma sources together with
penetrating diagnostics are the critical components to fundamental tests
of physical theories concerning the connection between microscopic and
macroscopic plasma behavior. Questions on the microscale relate to
particle dynamics and field coupling. On the mesoscale are processes
which link macro and microscale phenomena. Processes in this class
include turbulence, self-organization, chaos, mode conversion, and other
nonlinear and non-resonant wave interaction phenomena. Macroscale
phenomena are similarly rich and diverse. A fresh opportunity exists
in physics to understand connections, through more than just a simplistic
reduction, between microscale phenomena, which can be addressed through
well-known force laws, and macroscale phenomena which are very familiar
but which lack a fundamental description. What are the basic principles
which govern plasma dynamics at all scales? Some principles have been
empirically determined, but with uncertain ranges of validity. Mesoscale
phenomena are critical to the development of a more complete and coherent
picture of plasma physics and to its application in a large array of
critical technological areas.

YOU are an important part of this plasma dialogue

The dialogue for the Plasma Science & Technology Initiative
began in June, 1994 with a small one-day workshop held in Sante Fe,
New Mexico during the International Conference on Plasma Science.
An interactive dialogue with the internet USENET newsgroup
"sci.physics.plasma" begins in July, 1994. This is intended to be a
fully open dialogue, from specific suggestions for experiments and
instrumentation to planning and overall philosophy. Perhaps this
dialogue could contribute to multiple initiatives in various countries
with varying levels of coordination - the potential is great if there
is active participation in this internet dialogue - use your imagination!
Important consequences for industry could include both direct
applications in such areas as microelectronics, materials processing,
and microwave devices (see posted list of subject areas in plasma science
and technology with over 80 application topics), as well as the transfer
to industry of new plasma sources, measurements and characterization
methods developed in the laboratory and advanced computer modeling and
simulation tools as well.

[Prepared by Tim Eastman, University of Maryland, based on
preliminary draft by Tim Eastman, Chuan Liu, Hans Griem, Fred Skiff,
and William Destler of the Univ. of Maryland, and Walter Gekelman of
the University of California at Los Angeles (UCLA)]