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Topic Name: Goal of high-yield fusion reactor
Category: Electrical
Research persons: Bill Fowler,,Dillon McDaniel,Craig Olson, Alexander Kim,Boris Kovalchuk,Dillon McDaniel,Mike Mazarakis,Bill Fowler and Robin Sharpe
Location: Sandia National Laboratories,PO Box 969,Livermore, CA 94551-0969, United States
Details
An electrical circuit that should carry
enough power to produce the long-sought goal of controlled high-yield nuclear
fusion and, equally important, do it every 10 seconds, has undergone extensive
preliminary experiments and computer simulations at Sandia National
Laboratories’ Z machine facility.Z, when it fires, is already the largest
producer of X-rays on Earth and has been used to produce fusion neutrons. But
rapid bursts are necessary for future generating plants to produce electrical
power from sea water. This had not been thought achievable till now.
Sandia is a National Nuclear Security
Administration laboratory.
How does it work?
An automobile engine that fired one cylinder
and then waited hours before firing again wouldn’t take a car very far.
Similarly, a machine to provide humanity
unlimited electrical energy from cheap, abundant seawater can’t fire once and
quit for the day. It must deliver energy to fuse pellets of hydrogen every 10
seconds and keep that pace up for millions of shots between maintenance — a kind
of an internal combustion engine for nuclear fusion. That’s so, at least, for
the fusion method at Sandia National Laboratories’ Z machine and elsewhere known
as inertial confinement.
But, unable to produce fusion except
episodically, the method has been overshadowed by the technique called magnetic
confinement — a method that uses a magnetic field to enclose a continuous fusion
reaction from which to draw power.
The electrical circuit emerging from the
technological hills may change the balance between these systems. Tagged as
“revolutionary” by ordinarily conservative researchers, it may close the gap
between the two methods.
The circuit is easily able to fire every 10.2
seconds in brief, powerful bursts.
“This is the most significant advance in
primary power generation in many decades,” says Keith Matzen, director of
Sandia’s Pulsed Power Center.
The new system, called a linear transformer
driver (LTD), was created by researchers at the Institute of High Current
Electronics in Tomsk, Russia, in collaboration with colleagues at Sandia.
Says Rick Stulen, Sandia Vice President for
Science, Technology and Research Foundations, “This new technology not only
represents a remarkable technical advance but also demonstrates the strong
engagement of Sandia's scientists and engineers in the international community.”
The large-cherry-lifesaver path to
nuclear fusion
The circuit — a switch tightly coupled to two
capacitors — is about the size of a shoebox and is termed a “brick.” When bricks
are tightly packed in groups of 20 and electrically connected in parallel in a
circular container resembling a large cherry lifesaver, the aggregate, or
“cavity” as the physicists would have it, can transmit a current of 0.5
megamperes at 100 kilovolts.
A test cavity in Sandia’s Technical Area 4
has fired without flaw more than 11,000 times.
Because the cavities are modular, they can be
stacked like donuts on a metal prong called a stalk. Arranged in a suitable
configuration, they could generate 60 megamperes and six megavolts of electrical
power, enough (theoretically) to generate high-yield nuclear fusion within the
parameters necessary to run an electrical power plant.
“This is a revolutionary advance,” says Craig
Olson, Sandia senior scientist and manager of the pulsed power inertial fusion
energy program.
The next-generation cavity model, now being
tested in Tomsk, transmits 1.0 megamperes at the same voltage and with the same
rapidity. Five such units have been built; four have been purchased by Sandia,
and one by the University of Michigan. The units cost $160,000 each. They too,
according to Sandia scientist and project leader Mike Mazarakis, who supervised
the tests at the Siberian site, are performing without flaw.
“This is an amazing achievement,” says Sandia
Vice President Gerry Yonas, a former leader at Z and of Sandia’s Advanced
Concepts Group.
Advantages of the new technology
Happily for Sandia accountants but sadly to
those who love the widely distributed arcs-and-sparks photo of Z firing by
Sandia photographer Randy Montoya, the new switch eliminates the need for the
hundreds of thousands of gallons of insulating water and oil carried by the
present Z structure. It was over the surface of that water that the electrical
arcing of Z became a phenomenon as much appreciated by graphic artists as it was
loathed by engineers (who saw it as wasted energy). Also gone will be much of
Z’s intricate switching. All were needed to shorten to nanoseconds the machine’s
original microsecond pulse.
The linear transformer driver produces its
100-nanosecond pulse from the get-go. It works so well because its design lowers
inductances that ordinarily slow electrical transmission.
It does this in part by eliminating the huge
plates and extensive wiring in the current Z machine, all of which generate
magnetic fields. In the new system, each brick has almost no wiring. Two
capacitors about the size of small thermos bottles are tightly linked to a
switch the size of a lunchbox. There is little opportunity to generate magnetic
fields that slow the passage of current.
Further, linking the bricks in parallel in a
cavity not only adds currents, but decreases inductances to levels significantly
less than previously possible.
The subsets are then linked in series to add
voltages.
This allows a very powerful machine to fire
very rapidly, with only a thin layer of oil bathing the rings and rows of
switches.
The LTD technology is 50 percent more
efficient than current Z machine firings, in terms of the ratio of useful energy
out to energy in. Z is currently 15 percent efficient to its load (already a
very high efficiency among possible fusion machines).
There is, however, a small matter of cost.
Funding for Z historically has been for
defense purposes: Its experiments are used to generate data for simulations on
supercomputers that help maintain the strength, effectiveness, and safety of the
US nuclear deterrent. Even without its rapid repetition capability, a powerful
LTD machine would better simulate conditions created by nuclear weapons, so that
data from the laboratory-created explosion of Z firing could be used with
greater certainty in computer simulations regarding nuclear weapons. The US has
refrained from actual testing of nuclear weapons for 15 years.
But fired repeatedly, the machine could well
be the fusion machine that could form the basis of an electrical generating
plant only two decades away. Progress in this arena might eventually require
funding from DOE’s energy arm.
To confirm the new Z concept would take $35
million over five to seven years to build a test bed with 100 cavities. If
successful, future generations of Z-like facilities would be constructed with
LTDs.
Funding thus far has come from two US
Congressional Initiatives through DOE-NNSA Defense Programs, Sandia’s internal
Laboratory Directed Research and Development monies, and Sandia’s Inertial
Confinement Fusion program.
“It’s like building a tinker toy,” says
Matzen. “We think we need 60 megamperes to make large fusion yields. But though
our simulations show it can be done, we won’t know for certain until we actually
build it.”
The device was designed by Tomsk pulsed-power
head Alexander Kim with the switch developed by Boris Kovalchuk; its speed-up
from a microsecond to 100 nanosecond firing was urged by Sandia manager Dillon
McDaniel, and encouraged by Sandia managers Rick Spielman and Ken Struve; the
work was led at Sandia and Tomsk by Sandia researcher Mike Mazarakis; testing at
Sandia was by Bill Fowler and Robin Sharpe; the Z-IFE fusion energy program at
Sandia was initiated and is managed by Craig Olson.
Recent results on LTD development will be
presented at the IEEE International Pulsed Power Conference and the IEEE
Symposium on Fusion Engineering to be held in Albuquerque in June 2007.
Sandia has filed a patent application on a
high-power pulsed-power accelerator invented by William Stygar that can use an
LTD as the primary power generator to replace the conventional Marx generator
In Images:
1.Sandians
Dillon McDaniel (second from left) and Steve Glover (right) with Alexandar Kim
(HCEI, Tomsk, Russia) examine a 500- kilo-amp LTD for final check-out before
shipment from Siberia to Sandia (person on far left is Sandia-hired interpreter;
Roman Kahn). The LTD has been in testing at Sandia for the last 2.5 year
2.Boris
Kovalchuck (HCEI, in gray suit) demonstrates design of a new LTD system to
Sandian Dillion McDaniel as Alexander Kim looks on.
3.Dillon
McDaniel examines insulators that go between capacitor layers for 250, 500, and
1000 kilo-amp LTDs.
4.From
Siberia, not Area 51: Sandia researcher Bill Fowler tests circuits on an LTD
device able to produce large electrical impulses rapidly and repeatedly.
Funded:
Funding thus far has come from two US
Congressional Initiatives through DOE-NNSA Defense Programs, Sandia’s internal
Laboratory Directed Research and Development monies, and Sandia’s Inertial
Confinement Fusion program
Sandia is a multiprogram laboratory operated
by Sandia Corporation, a Lockheed Martin company, for the U.S. Department of
Energy’s National Nuclear Security Administration. Sandia has major R&D
responsibilities in national security, energy and environmental technologies,
and economic competitiveness
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