The 35 Tesla Resistive Magnet

Vital Statistics Strength 35 tesla Type Resistive Bore size 32 mm (~1.25 inches) Online since December 2005 Cost $0.5 million Weight 2,500 kg (2.75 tons) Height 1.52 meters (~5 feet) Water used per minute 139 liters (~37 gallons) Power required 19.6 MW

Overview

This is the world’s most powerful resistive magnet. Resistive magnets are also called “powered” or “bitter” magnets.

Designed and built on site, this magnet was upgraded in 2005 from 30 tesla. When it reached the 35 tesla mark, it surpassed the existing world-record resistive magnet, the Mag Lab’s 33 tesla instrument, which remains in use at the lab.

Unlike superconducting magnets, which can be unplugged after first being powered up, this magnet needs LOTS of electricity to generate its high magnetic field.

Mag Lab engineer Jack Toth examines a bitter plate.

Like the other resistive magnets here, the 35 tesla is constructed of hundreds of flat, round sheets of metal stacked one on top of the other. Made of high-strength copper alloys, these plates can withstand both the pressure resulting from high magnetic fields and the heat resulting from the 19.6 MW of electrical power that make it run. These plates are called Florida Bitter plates – “Bitter” after the fellow who invented them in 1936 (Francis Bitter), and “Florida” in honor of the Mag Lab scientists who greatly improved on Bitter’s design, which enabled the creation of more powerful magnets like the 35 tesla. The magnetic field is concentrated in the big hole in the middle of the plates; that’s where researchers put their experiments. The smaller holes allow the cold water that keeps the magnet from overheating to run through – at a speed of 45 miles per hour.

This magnet is generally used for condensed matter physics (basic materials science).

Links

For scientists:
• Users Hub: The 35 Tesla Magnet

For the general public:
• Magnets from Mini to Mighty