Nature’s Blueprint for Plasma Confinement

Plasma is the fourth state of matter – it is a substance made up of ionised, or charged, particles. Plasma is one of the most abundant states of matter in the universe, making up stars like our sun. Here on earth, you can find plasma in the Aurora Borealis and Auora Australis, as well as lightning. We can also artificially generate plasma to varying degrees of temperature and density – everything from modern flat-screen TVs to fluorescent lights to neon signs.

Plasma is also integral to fusion. Supporting fusion-relevant plasmas, however, is extremely challenging. Particles need to be heated to 100s of millions of degrees Celsius, and the machines capable of facilitating these conditions are extremely difficult to build. Because plasma is ionised matter it is made up of charged particles, and so we can use magnetic fields to control it.

The levitated dipole represents one of nature's most elegant solutions to plasma confinement. Just as earth’s magnetic field can trap and hold plasma in stable configurations, the levitated dipole reactor harnesses these same physical principles in a laboratory setting.

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Core Ideas

Earth and other planets have a plasma that surrounds them – known as the magnetosphere.
These plasmas have properties that would make an attractive fusion device if they could be replicated in a lab‑sized device.
Unique to dipole physics, the turbulence that naturally occurs in plasma benefits its performance, rather than degrade it.

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In Detail

Observations of the magnetosphere around earth prompted the late Professor Akira Hasegawa in 1987¹ to propose the idea of a dipole-based fusion reactor. Hasegawa noted that by levitating a magnet in the center of a large vacuum vessel, fluctuations in the plasma at the edge of the device should lead to plasmas where the temperature and density naturally increase towards the core of the device.

Like in magnetospheres, these temperature and density gradients are the result of plasma turbulence, which in other fusion concepts degrades plasma confinement as it causes energy, and therefore heat, to be lost. In the dipole, this turbulence is a welcome and necessary ingredient to support fusion-relevant plasma temperature and density gradients.

Hasegawa proposed an experiment to test if these attractive properties of astrophysical dipole plasmas would also hold true in a laboratory-sized “levitated dipole” device. If true, the overall simplicity of the device would make it an attractive fusion reactor concept, free of many of the issues that have challenged other fusion concepts to date.

¹A. Hasegawa, Comments Plasma Phys. Controlled Fusion, 1987, Vol. 11, No. 3, pp. 147-151.

Nature’s Blueprint for Plasma Confinement

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