New world record magnetic field achieved

Magnetic fields with high field strengths are needed for numerous solid state studies and are particularly important for use in sustained nuclear fusion. It is believed that magnetic field strengths of 1,000 tesla are needed to achieve this.

The generation of ultrahigh magnetic fields is always accompanied by internal stresses, sometimes strong enough to tear apart the instrument. A magnetic field of 1,200 T, for example, corresponds to nearly 60 tons of force per square millimeter, an amount that is nearly impossible to contain. To protect against this and produce reliable magnetic fields useful for precise physical measurements, it is crucial to generate them over a volume of at least one cubic centimeter.

In their article, Nakamura et al. generate ultrahigh magnetic fields using the electromagnetic flux-compression (EMFC) technique. Here, a thin metal cylinder called the “liner” undergoes a high-speed implosion when it’s accelerated by a magnetic force; the implosion is induced by a large electric current around its circumference that comes from a bank of condenser units. A seed magnetic field is initially generated in a large volume — about 500 cubic centimeters — and compressed by the implosion into a small space. This produces a megagauss magnetic field.

In this advance, energy is transferred more efficiently from condenser banks to the liner than was previously possible. The resulting implosion accelerated the liner to a speed greater than 5 kilometers per second, generating a magnetic field of 1,200 tesla, a world record for magnetic fields generated indoors in a controlled manner, rather than outdoors where chemical explosives have been used to accelerate the liner. This could have implications for nuclear fusion technology, so could turn out to be an extremely important result.

Source: “Record indoor magnetic field of 1200 T generated by electromagnetic flux-compression,” by D. Nakamura, A. Ikeda, H. Sawabe, Y. H. Matsuda, and S. Takeyama, Review of Scientific Instruments (2018). The article can be accessed at https://doi.org/10.1063/1.5044557 .