![graph showing plasma flow](images/59.jpg) |
Without
plasma flow (left); with plasma
flow (right). |
Plasma science (the study of ionized
gases) is critical to the development
of fusion energy (involving the fusion
of nuclei), which could be an abundant
energy source in the future. Efficient
confinement of hot plasma, which is
necessary to create fusion energy,
is prevented by small-scale instabilities
that cause turbulence. Office of Science
support has played a major role in
efforts to understand and reduce plasma
turbulence. U.S. researchers have
demonstrated that flow shear (radially
varying plasma flow velocities) can
suppress the turbulence responsible
for transporting particles and energy
across the magnetic field in fusion
devices. Experimental, theoretical,
and computer simulation studies have
shown that flow shear produces localized,
sharply defined transport barriers
that alter the physics of energy and
particle transport. The first improved
plasma confinement mode resulting
from the onset of a sharply defined
transport barrier was discovered by
German researchers in the early 1980s.
More recently, U.S. researchers identified
flow shear as the mechanism that produces
this edge transport barrier. Sheared
flows also have been shown to play
a dominant role in the formation of
other plasma confinement modes.
Scientific Impact:
The enhanced confinement regimes resulting
from flow shear stabilization of turbulence
are of considerable scientific interest;
systems seldom self-organize to a
higher energy state, with reduced
turbulence and transport, when an
additional source of free energy is
applied.
Social Impact: These
advances will help promote the availability
of fusion as an inexhaustible, safe,
and environmentally attractive energy
source. In addition to the general
public, beneficiaries may include
industries that use plasma science
and technology, including makers of
semiconductors and space propulsion
systems.
Reference: Z. Lin,
et al., Science, 281, 1835
(1998)
"Comparisons and Physics Basis of
Tokamak Transport Models and Turbulence
Simulations," A. M. Dimits, G. Bateman,
M. A. Beer, B. I. Cohen, ..., Phys.
Plasmas 7, 969 (2000)
URL:
http://fusion.gat.com/theory/pmp/
Technical Contact:
Steve Eckstrand, Research Division,
301-903-5546
Press Contact: Jeff
Sherwood, DOE Office of Public Affairs,
202-586-5806
SC-Funding Office:
Office of Fusion Energy Sciences |