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Topic Name: Controlled nuclear fusion and unlimited energy .
Category: Nuclear
Research persons: Daniel Dolan
Location: Sandia National Laboratories, ,PO Box 969,Livermore, CA 94551-0969, United States
Details
Sandia’s
huge Z machine, which generates temperatures hotter than the sun, has turned
water to ice in nanoseconds.
However, don’t expect anything commercial just
yet: the ice is hotter than the boiling point of water.
“The three phases of water as we know them —
cold ice, room temperature liquid, and hot vapor — are actually only a small
part of water’s repertory of states,” says Sandia researcher Daniel Dolan.
“Compressing water customarily heats it. But under extreme compression, it is
easier for dense water to enter its solid phase [ice] than maintain the more
energetic liquid phase [water].”
Sandia is a
National Nuclear Security Administration (NNSA) laboratory.
In the Z experiment, the volume of water shrank
abruptly and discontinuously, consistent with the formation of almost every
known form of ice except the ordinary kind, which expands. (One might wonder why
this ice shrank instead of expanding, given the common experience of frozen
water expanding to wreck garden hoses left out over winter. The answer is that
only “ordinary” ice expands when water freezes. There are at least 11 other
known forms of ice occurring at a variety of temperatures and pressures.)
“This work,” says Dolan, “is a basic science
study that helps us understand materials at extreme conditions.”
But it has potential practical value. The work,
which appears online March 11 in Nature Physics, was undertaken partly
because phase diagrams that predict water’s state at different temperatures and
pressures are not always correct — a fact worrisome to experimentalists working
at extreme conditions, as well as those having to work at distances where direct
measurement is impractical. For example, work reported some months ago at Z
demonstrated that astronomers’ ideas about the state of water on the planet
Neptune were probably incorrect.
Closer at hand, water in a glass could be cooled
below freezing and remain water, in what is called a supercooled state.
Accurate knowledge of water’s behavior is
potentially important for Z because the 20-million-ampere electrical pulses the
accelerator sends through water compress that liquid. Ordinarily, the water acts
as an insulator and as a switch. But because the machine is being refurbished
with more modern and thus more powerful equipment, questions about water’s
behavior at extreme conditions are of increasing interest to help avoid
equipment failure for the machine or its more powerful successors, should those
be built.
One unforeseen result of Dolan’s test was that
the water froze so rapidly. The freezing process as it is customarily observed
requires many seconds at the very least.
The answer, says Dolan, seems to be that very
fast compression causes very fast freezing. At Z and also at Sandia’s nearby
STAR (Shock Thermodynamic Applied Research) gas gun facility, thin water samples
were compressed to pressures of 50,000-120,000 atmospheres in less than 100
nanoseconds. Under such pressures, water appears to transform to ice VII, a
phase of water first discovered by Nobel laureate Percy Bridgman in the 1930s.
The compressed water appeared to solidify into ice within a few nanoseconds.
Ice VII has nothing to do with ice-nine, an
entirely fictional creation of author Kurt Vonnegut in his 1963 novel Cat’s
Cradle. There, a few molecules of the invented substance acts as a
precipitating seed to cause an extended chemical reaction that freezes almost
all of Earth’s water. Ice VII, on the other hand, only stays frozen as long as
it is under enormous pressure. The pressure relenting, the ice changes back to
ordinary water.
Nucleating agents, of course, are often used to
hasten sluggish chemical processes, such as when clouds are “seeded” with silver
iodide to induce rain. Dolan already had demonstrated, as a graduate physics
student at Washington State University, that water can freeze on nanosecond time
scales in the presence of a nucleating agent.
However, the behavior of pure water under high
pressure remained a mystery.
Sandia
instruments observed the unnucleated water becoming rapidly opaque — a sign of
ice formation in which water and ice coexist — as pressure increased. At the
70,000 atmosphere mark and thereafter, the water became clear, a sign that the
container now held entirely ice.
“Apparently it’s virtually impossible to keep
water from freezing at pressures beyond 70,000 atmospheres,” Dolan says.
For these tests, Z created the proper conditions
by magnetic compression. Twenty million amperes of electricity passed through a
small aluminum chamber, creating a magnetic field that isentropically compressed
aluminum plates roughly 5.5 by 2 inches in cross section. This created a
shockless but rapidly increasing compression across a 25-micron-deep packet of
water.
The multipurpose Z machine, whose main use is to
produce data to improve the safety and reliability of the US nuclear deterrent,
has compressed spherical capsules of hydrogen isotopes to release neutrons — the
prerequisite for controlled nuclear fusion and essentially unlimited energy for
humanity.
FUNDING & RESEARCH INSTITUTION:
This work is sponsored by the NNSA. Other
authors on the paper are Chris Deeney (now at NNSA), and Sandians Mark Knudson
and Clint Hall.
Sandia works
closely with industry, small business, universities, and government agencies to
bring new technologies to the marketplace. Discover how to leverage the
resources of a national laboratory for your benefit. Sandia has been
transferring technology to external partners for more than three decades,
especially where such agreements benefit Sandia’s primary mission for the
Department of Energy.
For questions or comments, contact
partnerships@sandia.gov, or call
(505) 284-2001.
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