Lawrence Today magazine, Spring 2004
A curious visitor peering through the glass
of Room 044 in the basement of Science Hall and seeing the large, elevated
aluminum
drum,
its
wide sides
wrapped
with thick, black bundles of wire amid an array of other tubes and hoses, might
conclude they had just stumbled upon an industrial-strength washing machine.
Or perhaps a remnant of eccentric “Doc” Brown’s Back
to the Future workshop.
Far from being a fancy Maytag or a mad-scientist movie prop, the item in question
is the cornerstone of Associate Professor of Physics Matthew
Stoneking’s
research. The drum, a toroidal vacuum chamber, which Stoneking brought with
him from his research
associate days at the University of Wisconsin, is at the heart of his work
on pure electron plasmas.
Thanks to a three-year, $178,000 grant from the National Science Foundation,
he soon will begin constructing a new and greatly improved apparatus, permitting
more sophisticated experimentation. The grant will enable him, in conjunction
with Lawrence physics students, to build a less imposing, but much more precisely
designed and constructed vacuum chamber out of stainless steel and copper in
his new laboratory in the recently renovated Youngchild Hall.
Pure electron plasmas are collections or “clouds” of electrons
confined in a vacuum chamber using magnetic and electric fields. Stoneking’s
research focuses on the criteria needed for confining a stable electron plasma
in a toroidal — doughnut-shaped — magnetic field and the factors
that limit the duration of the confinement in such systems.
A toroidal magnetic field can be visualized as a bundle of lines wrapped into
a circular loop, allowing charged particles, such as electrons, to stream or
flow along those lines like beads on a wire.
Plasma physics is the scientific foundation for the potential future production
of electric power by nuclear fusion, Stoneking says.
"Although they do not occur in nature, electron plasmas have proved to be excellent
systems for testing our understanding of the behavior of ‘complex’ fluids,” he
adds. “They can serve as a kind of ‘wind tunnel’ for testing
mathematical theories of fluid dynamics.”
In earlier experiments, Stoneking successfully confined electron plasmas in
a toroidal magnetic field for as long as two one-hundredths of a second (or
20 milliseconds). He estimates the new chamber will improve the purity of the
vacuum by approximately 100 times and strengthen the magnetic field by a factor
of five, resulting
in confinement times approaching one second. Durations of that
length would provide a more refined comparison of experimental results with
existing theoretical predictions.
The NSF grant will also underwrite summer research and provide travel stipends
for Stoneking and his students to attend national physics conferences. In addition,
it supplies Stoneking with funds to establish a collaboration with physics
colleagues at the University of California, San Diego.
This is the third grant Stoneking has received in support of his research since
joining the Lawrence physics department in 1997.