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Today, strangely enough, the field of laboratory astrophysics is being
paced by large experiments intended to delve in the physics of nuclear
weapons. The reason is that both energetic space-plasma phenomena and
nuclear weapons belong to a class of science called high-energy-density
physics. New experimental techniques, improved simulation codes, and
experimental diagnostics developed for the US Department of Energy's
program to keep the nation's arsenal of nuclear weapons safe, secure,
and reliable in the absence of underground testing are indirectly
benefiting our understanding of the universe.

The experiments are at the cutting edge to technology and physics and
involve both intense laser beams and pulsed-power facilities. The most
powerful laser project under construction is the National Ignition
Facility, a $1.2 billion facility slated for completion in 2003, in
which the beam from 196 lasers will deliver nearly 2 megajoules of power
to a millimeter-sized target, reproducing the temperatures within stars.

Plasma astrophysics is currently being done with machines called
pulsed-power generators, which currently operate in the 0.5-2 megajoules
range and are located at Sandia National Laboratories and Los Alamos
National Laboratory. Under construction is Atlas, a large pulsed power
generator for studying instabilities in the various states of matter.
Also mentioned is X-1, a 20-megajoule behemoth , so called after the
bright source in the constellation Cygnus A. An appreciable fraction of
machine usage for these large machines will be devoted to plasma
astrophysics.

Pulsed-power generators are the most prolific sources of microwaves and
X rays on Earth. They produce radiation through the interaction of
filamentary plasmas created when megavolts of electrical energy
discharge through centimeter-long arrays of wires. The energy pulses are
so powerful that the wires are rapidly vaporized and ionized into

plasma filaments that release a full spectrum of electromagnetic energy.

In addition, the current coursing through the plasma of ionized wire
induces the Z-pinch effect, in which a powerful current in a plasma in
pinched into a filament by the magnetic field produced by the current.
In the laboratory, the currents flow from energy stored in many
capacitors, while in the universe, cells of differing types of plasmas
are thought to play the role of the energy-storing capacitors. Thus,
from laboratory astrophysics experiments we may infer the structure of
the universe.

The X-ray spectrum of the universe (from 1 to 140 angstroms) allows an
in-depth study and comparison of the spectra produced by laboratory Z
pinches. In particular, X-ray spectroscopy, the study of the absorption
and emission of X rays, can yield significant data on the chemical
compositions, temperatures,, densities, and magnetization for the plasma
universe. The launching of three X ray observatories started in 1999
will increase the number and resolution of X-ray charts of the plasma
universe, helping to map regions of energy storage, areas of release,
and the electrical currents required in transport.

*/—A. P. and G. C. S/*.

Filamentary electrical currents produced deep inside the Sandia National
Laboratories "Z" machine shown here represent the morphology that may be
expected in either laboratory astrophysics experiments or the structure
of the universe itself.

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