World's Most Powerful Magnet Tested Ushers in New Era for Steady High Field Research
December 17, 1999
Janet Patten, (850) 644-9651
TALLAHASSEE, Fla. – A team of researchers from the National High Magnetic Field Laboratory (NHMFL) conducted the first research in continuous magnetic fields of 45 tesla (one million times the Earth's magnetic field) in the new hybrid magnet on December 12. The hybrid magnet represents one of the crown jewels of this national user facility. The NHMFL has achieved its goal from the National Science Foundation of delivering continuous fields of 45 tesla.
The 45 tesla hybrid magnet consists of two behemoth magnets. The total magnet system weighs 34 tons and stands 22 feet tall. An enormous superconducting magnet forms the outside layer and is the largest cable-in-conduit magnet ever built and operated to such high field. It is cooled to within a few degrees of absolute zero with the only operating superfluid helium cryogenic system built for magnet applications in the United States. A very large resistive magnet (electromagnet) sits in the center of the superconducting magnet. The two magnets work in tandem to provide the most intense constant magnetic field on Earth. This new magnetic field strength gives scientists a new scale of magnetic energy to create new states of matter and probe deeper into electronic and magnetic materials than ever before.
"The scale and complexity of bringing two different magnet technologies into one working system with the necessary power, cooling, and control components represents an engineering milestone," stated NHMFL Director Jack Crow. "It is like building the Space Station, you have many parts being manufactured by different groups and when they are all brought together everything must fit and work in unison," he added. After a few optimization activities to be conducted on the hybrid, it is anticipated that the magnet will reach beyond 45 tesla.
Researchers conducting the first experiment in the hybrid magnet said, "The experience was like being on the Wright Brothers first flight. But instead of hanging on for dear life, it was more like a trans-Atlantic flight on the Concord. The 45 tesla hybrid magnet adds another champion thoroughbred to the existing NHMFL stable of race horses."
The first hybrid experiment consisted of four samples of materials representing many aspects of condensed matter physics: an exotic organic metal, a curious magnetic "bad-metal", a thin-layered semiconductor, and a semiconductor device. In very general terms, the materials that make up our world and underpin our modern technologies undergo transformations that make them behave very differently in intense magnetic fields. Although the data from the experiment is still being carefully analyzed, initial findings show some interesting new physics. At high magnetic fields between 35 and 45 tesla the exotic metal "morphs" from one state to another. Above 38 tesla the "bad metal" becomes a "good metal". Finally, the semiconductor systems, which show something called the quantum Hall effect (which has yielded two Nobel prizes in the 1990's), showed beautifully complex behavior, switching between conducting and quantum non-conducting states as the field was increased. Researchers were intrigued as they watched the evolution of a "fractional 1/3 quantum Hall state" in fields between 32 and 40 tesla.
Although the 45 tesla hybrid magnet is a gigantic structure reaching over two stories high, the chamber where the experiments are conducted and the research samples are extremely small. The just completed hybrid experiment had four materials positioned on a single probe with four to ten electrical leads attached to a tiny platform no thicker than a matchbook cover and no bigger in diameter than a #2 pencil. The entire assembly was mounted inside a tall, narrow thermos bottle-like container to keep the samples below 5 degrees above absolute zero. The container was carefully lowered into the narrow (an inch and a quarter) central tube of the hybrid magnet.
As the magnet is brought up to full field, the electrons and nuclei within the samples experience dizzy spins, and some electrons may execute fantastic orbits like being at an amusement park, or fly around as if they are inside a powerful pinball machine. Researchers at the NHMFL are then able to follow these bizarre antics--that happen at speeds 1000 times faster than the speed of sound--with sophisticated electronic and computer equipment. Later the data is deciphered and analyzed to explore the rich characteristics of these complex structures.
Many of the scientists using the facilities at the NHMFL are studying materials and related areas. Large research magnets are giant microscopes that look at materials like no other scientific tool, in order to examine what is going on with atoms, molecules, nuclei, and electrons. These materials come in all sizes, colors, and shapes and most of them surround our daily lives. From the refrigerator motor, to the magnet on its door, to the ice that forms in its freezer, to the filaments that light its interior, to the gases that circulate in its coils, and its protective coating to keep it colder inside, most materials undergo extensive investigations before being applied to technologies.
The NHMFL is funded by the National Science Foundation and the State of Florida. It is operated by a consortium comprising of Florida State University, the University of Florida and Los Alamos National Laboratory. The NHMFL is a dedicated national users facility providing state-of-the-art magnets for research in all areas of science, including, biology, bio-medical, chemistry, geology, engineering, materials science, and physics. The NHMFL is the largest and highest-powered laboratory of its type in the world and the only one in the Western Hemisphere.