There’s a moment in any movie or cartoon featuring a mad scientist when they flip a switch or mix two chemicals and boom, their lab explodes and smoke billows out the windows and doors. In reality, at least in the modern era, lab explosions are discouraged. But a recent experiment with electromagnetism in Tokyo produced the strongest controlled magnetic field ever created, reports Samuel K. Moore at IEEE Spectrum, powerful enough to blow open the blast doors of the laboratory.
The big bang came when researchers at the University of Tokyo pumped 3.2 megajoules of electricity into a specially designed coil to produce a massive magnetic field. While the researchers were hoping that the field would reach 700 teslas, the unit used to measure magnetic flux density or informally, magnetic field strength. Instead, the field reached 1,200 teslas. That’s about 400 times stronger than the most powerful MRI machine, which produces three teslas. The resulting explosion bent up the iron cupboard the device was enclosed in and blasted open the metal doors.
“I designed the iron housing to endure against about 700 T,” physicist Shojiro Takeyama, senior author of the study in the journal Review of Scientific Instruments, tells Moore. “I didn’t expect it to be so high. Next time, I’ll make it stronger.”
Luckily, the researchers themselves were tucked away in a control room, protected from the blast.
So, what were Takeyama and his colleagues doing letting off massive magnetic booms in the middle of Tokyo? Rafi Letzer at LiveScience explains that scientists have been pursuing increasingly larger controlled magnetic fields for several decades. Takeyama has been trying to beat the 1,000-tesla level for the last 20 years, reaching the goal with this new device.
In essence, the electromagnet is a series of tubes consisting of a coil with a copper inner coil within it. When massive amounts of electricity are run through the coils, the inner coil collapses in on itself at a rate of Mach 15, which is over 3 miles per second. The magnetic field in the coil compresses tighter and tighter until it reaches incredibly high levels. Then, in a fraction of a second, the whole thing collapses, resulting in the explosion. With a little more engineering and some stronger doors, the team believes they could push their device to 1,800 teslas.
This was not the largest magnetic field ever generated by humans. Some super-strong fields are produced by lasers, but are so small and short-lived they are difficult to study or use. Takeyama tells Letzer that historically, American and Russian researchers have done some large-scale outdoor tests using high explosives packed around magnetic coils, producing fields up to 2,800 teslas. But these, too, are imperfect.
“They cannot conduct these experiments in indoor laboratories, so they usually conduct everything in the outdoors, like Siberia in a field or somewhere in a very wide place at Los Alamos [New Mexico],” he says. “And they try to make a scientific measurement, but because of these conditions, it's very hard to make precise measurements.”
The team’s tool, however, can be used in a controlled lab setting and produces a relatively large field, a little less than a nanometer, which is big enough to do some real science. According to a press release, the goal is to produce a controlled magnetic field that could be used by physicists. The hope is that the field can be controlled well enough that materials can be placed inside the tiny field so researchers can bring the electrons to their “quantum limit,” in which the particles are all in their ground state, revealing properties that researchers have yet to discover. In that case, bigger is better.
“In general, the higher the field, the resolution of measurement becomes better and better,” Takeyama tells Moore at IEEE.
The other possible application—once they get the explosions worked out of the system—is use in fusion reactors, a type of energy-producing device in which plasma is held stable using a strong magnetic field as its hydrogen fuses, creating a reaction similar to that of the sun and producing almost limitless clean energy. According to the release, researchers believe they need to be able to control a 1,000-tesla magnetic field to produce sustained nuclear fusion.