Copper coating conceals nine layers of engineering intrigue
By Amy Mast
It's as slim as a piece of copy paper — just a tenth of a millimeter — but this wisp of coppery ribbon has a secret. It's actually made from nine super-thin layers that come together to form an innovative superconductor for the lab's newest magnet design.
What's in our nine-layer-dip of ribbon conductor that makes it so revolutionary? YBCO (short for yttrium barium copper oxide), an ingeniously engineered high-temperature superconductor, is the star of the show (see illustration below).
YBCO is manufactured by New York company SuperPower Inc. and is the key compound inside the lab's powerful, high-temperature all-superconducting magnet, which is being built right now by lab engineers and technicians. This family of magnets could eventually surpass strengths of 50 tesla —stronger than the lab's world-record 45-T hybrid magnet.
"This is a new form of conductor; it's difficult to work with, and we are learning all over again how to make magnets with this stuff," explained Mag Lab engineer Denis Markiewicz, who's at the helm of the YBCO magnet project. The first operational magnet using this technology is scheduled to debut in 2012. At 32 tesla, it will be 45 percent more powerful than the strongest superconducting magnets now in use.
YBCO itself makes up only one percent of the thickness of this coil — a single micron. (Look at this single page sideways and imagine it divided by one hundred.) That one-micron strip needs both strength and stability to function properly inside a research magnet, and that's where the other 99 percent comes in.
"To prevent the superconductor from burning out, you always need some normal conductors in the mix to go along with it," Markiewicz said. For starters, there's copper, which coats the entire outside and gives the coil its penny color. Nickel alloy, for strength, makes up about half of the coil's thickness. Several very thin buffer layers act to align the individual grains of YBCO and to protect it chemically.
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