Field Work: Research in Big Magnets is Hot and Getting Hotter
By Kristen Coyne
Way back in 600 B.C. the Greeks first noticed that
lodestone attracted iron; a few centuries later, the
Chinese began exploiting that knowledge to make
the earliest compasses. Since then, the science of electricity
and magnetism has come a long way, and men have devised
magnets exponentially more powerful than the natural ones
that first fascinated ancient minds.
Greg Boebinger.
Interest in big magnets endures in Asia, Europe and elsewhere,
where scientists and engineers are planning and building new
research institutions they hope will rival the biggest magnet lab
in the world, the National High Magnetic Field Laboratory.
There's good reason researchers are pushing hard for scarce
R&D euros, dollars, yuan and yen to build bigger and better
magnets: High magnetic fields can probe the structure and
behavior of matter like no other tool. Used alone or in tandem
with instruments such as mass spectrometers, lasers and MRI
machines, these magnets are both powerful and versatile,
with applications in physics, biology, chemistry,
geology, engineering and materials science.
Whatever the discipline, high-field
magnets make possible the kind of
heavy-hitting, basic research that
deepens our knowledge of the world
while drawing us closer to practical
applications that will improve the way
we live. Higher fields are in high demand
among researchers because bigger
magnets bring better results.
"It's true," said Greg
Boebinger, director of the
National High Magnetic
Field Laboratory, which
is headquartered at
Florida State University
in Tallahassee. "I can think of a half dozen countries around
the world that are now investing so much money in magnet
research that they will one day rival, or even surpass, some of
our best magnets."
Established by the National Science Foundation in 1990, the
"Mag Lab," as it's more commonly known, is home to some of the
biggest, strongest, most sought-after magnets on the planet.
The shiniest of its crown jewels is the hybrid magnet, a 35-ton
behemoth that produces the highest sustained magnetic field
in the world. Scientists measure magnetic strength in units
called tesla. A fridge magnet is a tiny fraction of a tesla. A 1-tesla
magnet can pick up a car, while a 3-tesla runs the average MRI
machine. The Mag Lab's hybrid, in comparison, produces a
phenomenal field of 45 tesla.
Clearly, today's research magnets are no lumps of lodestone. In
fact, they aren't permanent magnets (like those on the fridge)
at all, but rather electromagnets, superconducting magnets,
or combinations such as the hybrid. From the outside, they
look like Thermos bottles on steroids. Inside, they are highly
sophisticated instruments requiring great skill and resources to
operate. At the center of each sits some of the hottest real estate
in science: the magnet's bore. This empty space, measuring at
most a few inches in diameter, is where the action happens.
Scientists put their experiments in the bore then watch the data
roll in.
| Magnets at a Glance
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RESISTIVE magnets (also called Bitter magnets or electromagnets) require lots of
electricity and cooled water. Resistive magnets can reach and sustain high fields
over many hours, but they are costly to operate and use is limited by the amount of
power available.
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SUPERCONDUCTING magnets require little or no electrical power to run once they
are brought up to full field because they are made with superconducting materials
that conduct electricity without resistance as long as they are kept extremely
cold (as low as one degree above absolute zero temperature, depending on the
material). While they are cheaper to operate, the strength of field is limited by
properties of superconducting materials.
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HYBRID magnets combine resistive and superconducting technology, taking
advantage of the strengths of each; resistive coils are nested inside the
superconducting coils, the latter of which account for most of the magnet's weight
and volume. Hybrid magnets produce the highest sustained magnetic fields
possible. |
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PULSED magnets produce much higher fields (up to 89 tesla) than the other magnet
technologies, but the high field lasts only seconds or fractions of a second.
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SERIES CONNECTED HYBRID magnets, like the conventional hybrid magnets
described above, combine resistive and superconducting technology. But the series
connected magnets, currently being built, differ in that they are driven in series with
the same power supply, rather than independently. This creates the high fields using
less power.
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Contrary to what many might think, scientists don't use research
magnets to study magnetism. The magnets aren't the ends, but
the means – the means to discovery. Just as a microscope allows
us to view details invisible to the naked eye, so do magnetic
fields reveal the nature of things – and of the very laws of
science that account for them.
How can you "see" things with magnetic fields? X-ray machines
detect broken bones by using a type of energetic light that
shines right through your body.
Magnets also exploit electrons – the moving electrons that
make up their fields – to examine objects within that field.
It all comes down to atoms and the fact that so much of the
universe is governed by opposites that attract and like things
that repel. If you put something inside a magnet, the positive
and negative particles in its atoms interact with each other and
with the magnetic field in a way that reveals something about
its properties in particular, or about the properties of matter in
general.
Horst Störmer.
There are lots of questions you can answer with a magnet. For
example, what kind of materials will work best in tomorrow's
faster, smaller computers? What changes does a potential
Alzheimer's drug stimulate in the brain? What molecules make
up a sample of crude oil – and is it worth drilling for? What is the
best way to build a superconducting cable – and save untold
billions in electricity costs?
"High magnetic fields have always
been an essential tool in the tool box
of physicists," said Columbia University
physicist Horst Störmer, who shared
the 1998 Nobel Prize in Physics for
the discovery, made with the help of
high-field magnets, of a new form of
quantum fluids. "Nothing is comparable
to standing next to these giant, roaring
magnets, generating stable magnetic
fields higher than anywhere else on the
globe, and have data emerging that seem implausible at first,
but actually represent a new discovery in physics."
This is tantalizing stuff for scientists. That's why China is
spending some $50 million on its new High Magnetic Field
Lab, part of $750 million that country is investing in science
infrastructure. That is also why the Europeans are planning to
consolidate their four magnet labs (two in France, one each
in Germany and the Netherlands) under a single umbrella
institution, the European Magnetic Field Laboratory. Taking
a nod from the Mag Lab, which has sites at the Los Alamos
National Laboratory in New Mexico and the University of Florida
in Gainesville, the Europeans hope this multiple campus model
will eliminate duplication of effort and allow each facility to
produce its best research.
If there is a competitive aspect to these magnet development
efforts, there also is a lot of cooperation. International
collaboration can only further science, and few institutions offer
better living proof of this than the Mag Lab. Its staff is made up
of experts from around the world, and of the thousand scientists
who travel to the lab every year to conduct experiments, nearly
a quarter come from overseas.
A scientist's research can only be as good as her instruments.
Today's magnets have the highest fields that materials and
technology will allow. But stronger materials and more
advanced technologies now under development will lead to
even higher fields. These mightier magnets will extend scientific
techniques while lowering operating costs – which now run well
into the millions of dollars annually at the Mag Lab alone. That
incentive has pushed the Mag Lab to become one of the world's
leading designers and builders of magnets. With $20 million in
contracts and grants, the lab's engineers are currently building a
pair of series connected hybrid magnets, a novel design that will
reach higher fields with less electricity. One of these magnets,
funded by the NSF, will be located in the Mag Lab's Tallahassee
headquarters; the second is headed to Germany's Helmholtz
Centre Berlin, where it will be used for neutron scattering.
Myriam Sarachik.
The scientific community's appetite for knowledge extends
to other magnets as well. Under the auspices of the National
Academies, which advise the U.S. government and public on
science and technology issues, the Committee on Opportunities
in High Magnetic Field Science issued a report in 2005
underscoring the need for more powerful magnets. Noting
that "the prospects are bright for future gains from high-field
research," the report called specifically for the development
of a 30 tesla nuclear magnetic resonance (NMR) magnet, a 60
tesla hybrid magnet and a 100 tesla long pulse magnet – all
projects that will require the development of new materials and
interinstitutional collaborations.
Myriam Sarachik, a distinguished
professor of physics at City College of
New York, looks forward to the day
those tools open more new areas of
discovery for physicists, biologists
and other scientists. A member of the
National Academy of Sciences, Sarachik
said she hopes the U.S. can maintain its
impressive lead in high-field magnet
research: It's one of the scientific niches in which the country still holds a very strong leadership position. That leadership not only benefits U.S. science and
industry, she noted, but scientific collaborators across the globe.
"Other parts of the globe are slowly coming up to our level –
and not so slowly in some instances," said Sarachik. "These
unique high-field magnets have been a tremendous advantage
to the U.S. position in scientific research and innovation."
