Super-magnet sheds light on semiconductors

Split Florida Helix device can generate fields above 25 tesla

Robert Jaques, vnunet.com 01 Nov 2007

US researchers have demonstrated a revolutionary magnet design that could literally shed new light on nanoscience and semiconductor research.

Developed by engineers at Florida State University's National High Magnetic Field Laboratory, the Split Florida Helix magnet can direct and scatter laser light at a sample down the centre of the magnet and from four ports on the sides.

Due to become fully operational in 2010, the device can generate fields above 25 tesla. The highest-field split magnet in the world currently attains 18 tesla.

Tesla is a measurement of the strength of a magnetic field. One tesla is equal to 20,000 times the Earth's magnetic field.

The scientists will be able to expand the scope of their experimental approach, learning more about the intrinsic properties of materials by shining light on crystals from angles not previously available in such high magnetic fields.

"You have enough to worry about with traditional magnets, and then you try to cut huge holes from all four sides from which you can access the magnet," said lab engineer Jack Toth who is spearheading the project.

"Basically, near the midplane, more than half of the magnet structure is cut away for the access ports, and it is still supposed to work and make high magnetic fields."

Engineers have been trying to solve the problem of creating a magnet with side access at the midsection, but have met with little success in higher fields.

Magnets are created by packing together dense, high-performance copper alloys and running a current through them. But Toth explained that carving out empty space at the heart of a magnet presents a "huge" engineering challenge.

Instead of fashioning a tiny pinhole to create as little disruption as possible, as other labs have tried, Toth and his team created a design with four big elliptical ports crossing right through the midsection of the magnet.

The ports open 50 per cent of the total space available for experiments, a capability the laboratory's visiting scientists have long desired.

"It is different from any traditional magnet that we have built before, and even the fabrication of our new parts was very challenging," Toth said.