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The Culham Centre for Fusion Energy (CCFE) is partnering with a group of leading universities to advance understanding of one of the hottest topics in fusion research: turbulence in tokamak plasmas.

The £5 million-plus research program, funded by the Engineering and Physical Sciences Research Council (EPSRC), will be led by a consortium of universities with a strong fusion focus—York, Oxford, Strathclyde and Warwick—and will work in partnership with Culham.

A tokamak operates by using a strong magnetic field to hold the hot fusion fuel—which is in the plasma state—away from the reactor walls. In practice the plasma in tokamak experiments is highly turbulent, and this turbulence increases the loss of heat and particles, degrading the fusion performance. If the turbulence can be reduced, this could open the way to more compact or higher fusion power reactors.

As part of the new initiative, scientists will study how well the magnetic field can confine the plasma in CCFE's new MAST Upgrade spherical tokamak. They will also seek to shed further light on the properties of an insulating region that exists at the edge of most tokamak plasmas, including JET, called the pedestal region. This narrow region suppresses the loss of heat and fuel from the plasma, helping to raise the core pressure closer to fusion conditions. The more insulating the pedestal, the higher the central plasma pressure.

Read the full article on the CCFE website here.

--The MAST Upgrade control room (SMD Photography)

At the core of ITER's neutral beam heating system is a novel high-frequency ion source that has been under development for years at the Max Planck Institute for Plasma Physics (IPP) in Garching, Germany. In recent results that are significant for ITER, IPP's ELISE test rig has achieved the ion current required by ITER in hydrogen for 1,000 seconds.

Neutral beam injection relies on high-speed, high energy atoms that penetrate deep into the plasma and transfer their energy to plasma particles by means of collision. The large plasma volume at ITER will impose new requirements on this proven method of injection: the particles will have to move three to four times faster than in previous systems in order to penetrate far enough into the plasma, and at these higher rates the positively-charged ions become difficult to neutralize.

At ITER, for the first time, a negatively-charged ion source has been selected, based on the development of several generations of prototype negative ion sources at IPP.

Since 2009 IPP's ELISE test rig—half the size of what is projected for ITER—has been a valuable source of experimental data as it has advanced step by step to new orders of magnitude. In the most recent report, ELISE was able to produce a stable, homogenous negative ion beam for 1,000 seconds at ITER current strength.

In addition to further work on ELISE, IPP will be collaborating with teams at ITER's Neutral Beam Test Facility, where the full-scale ITER-scale negative ion source SPIDER was commissioned earlier this year.

Read the full report on the website of the Max Planck Institute for Plasma Physics.