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Among the most feared events in space physics are solar eruptions, massive explosions that hurl millions of tons of plasma gas and radiation into space. These outbursts can be deadly: if the first moon-landing mission had encountered one, the intense radiation could have been fatal to the astronauts. And when eruptions reach the magnetic field that surrounds the Earth, the contact can create geomagnetic storms that disrupt cell phone service, damage satellites and knock out power grids.

NASA is eager to know when an eruption is coming and when what looks like the start of an outburst is just a false alarm. Knowing the difference could affect the timing of future space missions such as journeys to Mars, and show when steps to protect satellites, power systems and other equipment need to be taken.

(Photo NASA)

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Scientists at the US Department of Energy's Princeton Plasma Physics Laboratory (PPPL) have produced self-consistent computer simulations that capture the evolution of an electric current inside fusion plasma without using a central electromagnet, or solenoid.

The simulations of the process, known as non-inductive current ramp-up, were performed using TRANSP, the gold-standard code developed at PPPL. The results were published in October 2015 in Nuclear Fusion. The research was supported by the DOE Office of Science.

In traditional donut-shaped tokamaks, a large solenoid runs down the centre of the reactor. By varying the electrical current in the solenoid scientists induce a current in the plasma. This current starts up the plasma and creates a second magnetic field that completes the forces that hold the hot, charged gas together.

But spherical tokamaks, a compact variety of fusion reactor that produces high plasma pressure with relatively low magnetic fields, have little room for solenoids. Spherical tokamaks look like cored apples and have a smaller central hole for the solenoid than conventional tokamaks do. Physicists, therefore, have been trying to find alternative methods for producing the current that starts the plasma and completes the magnetic field in spherical tokamaks. 

One such method is known as coaxial helicity injection (CHI). During CHI, researchers switch on an electric coil that runs beneath the tokamak. Above this coil is a gap that opens into the tokamak's vacuum vessel and circles the tokamak's floor. The switched-on electrical current produces a magnetic field that connects metal plates on either side of the gap.

Read more on the PPPL .

Momentum is building on the MAST Upgrade project at the Culham Centre for Fusion Energy (CCFE) in the UK.

When completed, the upgrade of the Mega Amp Spherical Tokamak (MAST) will enable scientists to test the spherical tokamak design as a candidate for a Component Test Facility that will trial technology and materials in advance of the next-step machine; add to the knowledge base for ITER on key plasma physics issues; and test a high-power exhaust system known as a Super-X divertor.

The final phase of assembly will take place in 2016.

See the three-minute video on the CCFE .