Tokamak breaks record

Engineers at MIT’s Plasma Science and Fusion Center in the US have set a world record for plasma pressure at the Institute’s Alcator C-Mod tokamak nuclear fusion reactor on its last day of operation.

This 360-degree picture shows inside the nuclear fusion reactor, which saw pressures rise to over 2 bar for the first time. While at first glance the pressure might seem underwhelming, being about that of an average car tyre, the temperature inside reached over 35x106 °C, approximately twice as hot as the centre of the sun.

The plasma produced 300 trillion fusion reactions per second and had a central magnetic field strength of 5.7 tesla. It carried 1.4 million amps of electrical current and was heated with over 4x106 watts of power. The reaction occurred in a volume of approximately 1m3 and lasted for two seconds.

Alcator C-Mod is the world’s only compact, high-magnetic-field fusion reactor with advanced shaping in a design called a tokamak, which confines the superheated plasma in a donut-shaped chamber.

C-Mod’s high-intensity magnetic field - up to 8 tesla - is 160,000 times the Earth’s magnetic field and is critical to creating the dense, hot plasmas by keeping them stable at more than 80x106 °C. Its magnetic field is more than double what is typically used in other designs, which quadruples its ability to contain the plasma pressure.

To understand how Alcator C-Mod’s design principles could be applied to power generation, MIT’s fusion group is working on adapting newly available high-field, high-temperature superconductors that will be capable of producing magnetic fields of even greater strength without consuming electricity or generating heat.

Justin Cunningham

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