World's Most Powerful Pulsed Magnet Dedicated

Los Alamos National Laboratory
CONTACT: John Gustafson, (505) 665-9197 / [email protected]

WORLD'S MOST POWERFUL PULSED MAGNET DEDICATED

LOS ALAMOS, N.M., Aug. 28, 1998 - A multi-ton magnet powered by a billion-watt generator and capable of creating powerful, pulsed magnetic fields for a longer period of time than any other in the world was commissioned today in ceremonies at the U.S. Department of Energy's Los Alamos National Laboratory.

"This magnet will revolutionize research in high magnetic fields," said Greg Boebinger, director of the National High Magnetic Field Laboratory's Los Alamos Center. "Its unprecedented flexibility offers researchers the chance to conduct standard, sensitive measurements in extremely intense magnetic fields that can only be provided by pulsed field magnets."

High magnetic fields offer scientists one of the most effective and noninvasive tools to explore basic and new materials critical to modern technology. Research areas include semiconductors, high-temperature superconductors, magnetic resonance imaging, complex chemical and biological structures, and magnetic materials used in computer, VCRs and CD players.

The National High Magnetic Field Laboratory, funded by the National Science Foundation, includes three separate campuses: at Los Alamos, the University of Florida and Florida State University.

Under the NHMFL consortium, Los Alamos offers researchers pulsed-field magnets and the facilities at the Florida universities offer sustained magnetic fields, magnetic imaging and ultra-low temperature capabilities.

"This multi-institutional Florida-New Mexico partnership has been extraordinarily productive in advancing high-field magnet research and technology and providing the best resources worldwide to the research communities of the United States," said NHMFL Director Jack Crow. "Today, we are recognizing another exciting plateau and I anxiously anticipate bold science that will be gleaned from this unique magnet system."

Dignitaries from the NSF, State of Florida, University of California and NHMFL attended today's commissioning ceremonies.

The pulsed-field magnet, consisting of nine nested electromagnetic coils wrapped in steel cylinders, can reach a peak field strength of 60 tesla, more than a million times greater than Earth's magnetic field. The magnet lab staff is finalizing operating procedures before opening the magnet to national users this fall, but trial experiments already are demonstrating the magnet's research potential.

Part of the magnet's uniqueness is that the shape of the magnetic field pulse can be tailored specifically to the needs of the experimenter. The field strength can be held constant at certain specified values, for example, or swept from zero to maximum strength, or taken through more complicated pulses, such as a stair-step pattern.

The magnet's ability to hold a constant magnetic field strength has enabled Los Alamos researchers and colleagues from the University of Florida and the University of California, Riverside, to make first-ever measurements of the heat capacity of materials in a pulsed-magnet system.

Heat capacity tells researchers about basic material properties, such as identifying phase transitions (because a material sheds or absorbs heat when going through a phase transition), the density of electronic states or stiffness of a crystallographic lattice. If the magnetic field is not steady, it will induce currents in a metallic material that will generate internal heat and corrupt the heat capacity measurement.

The research team, funded by an NHMFL research grant and led by Los Alamos' Roman Movshovich, built a calorimeter that delivers a specific pulse of heat into the material under study. The heat input can be synchronized precisely with the arrival of the magnetic pulse due to the programmable nature of the 60- tesla magnet.

"This was a high risk project," Movshovich said. "People were skeptical that we'd be able to make this measurement, and everybody was ecstatic when we got our data. It's a real tribute to the qualities of the magnet and the performance of the operations team."

"This magnet is truly unique," said Hong-wen Jiang, professor of physics at UCLA. Jiang and colleagues are studying the interactions of electrons and "holes" -- basically energy states that can absorb an electron -- in an advanced semiconductor material. The passage of electrons to and from holes is exploited to design better semiconductor devices, such as lasers and photo-detectors.

The researchers can take thousands of individual measurements during the second or so it takes the field to ramp up to its maximum strength of 60 tesla, squeezing the electronic orbits of a sample in an increasingly strong magnetic vice. These measurements provide insights into the quantum mechanical interactions that govern the material's electrical and optical properties.

"The magnet is like a tuning parameter that modifies the electron-hole interactions," Jiang said. "Its field reaches deep into the quantum regime for materials, where we can expect to see new phenomena."

"Pulsed magnetic field research at Los Alamos offers particularly exciting opportunities at this time," Boebinger said. "Experimental techniques in non- destructive pulsed fields are developing rapidly."

"We can expect many discoveries in this area since we are exploring physics in a new regime of parameters," Jiang said. At the same time, Jiang noted that the research is risky, in a sense, precisely because researchers are venturing into unknown territory. "The NHMFL has been very supportive of this work and willing to let us try new things," he said.

Developing the 60-tesla magnet was a challenge for engineers. The magnetic forces are so strong they want to rip apart the magnet, which is why the electromagnetic coils must be wrapped in steel blankets. The outer coil is large enough for a person or two to fit inside; the central core, where the samples are placed for study, is but a few inches across.

The magnet is cooled with liquid nitrogen to survive the tremendous heat generated when the massive generator -- large enough to power the state of New Mexico -- shoots its electric charge into the magnet. As the electricity circulates through the coils, it creates magnetic field lines concentrated at the center of the magnet.

When the generator unleashes its charge, "the magnet makes a screech that bears an uncanny resemblance to an angry Godzilla from the movies," Boebinger said. No loose metal can be left in the vicinity of the magnet when it is operating lest it get yanked violently into the magnet.

Magnets at the NHMFL will continue to intensify, since design of a 100-tesla magnet is now under way as a joint effort between the U.S. Department of Energy and the NSF.

Los Alamos National Laboratory is operated by the University of California for DOE.

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