W 7-X fusion experiment marks first hydrogen plasma

The Wendelstein 7-X experimental nuclear fusion device has passed a major milestone in its development with the generation of its first hydrogen plasma. W 7-X, at the Max Planck Institute for Plasma Physics (IPP) in Griefswald, Northeastern Germany, is a stellarator: a reactor shaped like a twisted doughnut, which confines the plasma in which fusion takes place within magnetic fields with a complex geometry.

W 7-X was completed last year, as The Engineer reported in our December on-line issue. Since then, its operators have performed 300 pulses inside the reactor with a plasma made from helium. These served to clean the inside of the vacuum chamber, which allowed the plasma temperature to be increased; it eventually reached 6million degrees Celsius. During this phase, the IPP team also tested W 7-X’s instruments, including X-ray spectrometers, interferometers, laser scattering and video diagnostics. “This makes everything ready for the next step,” commented project head Prof Thomas Klinger, “We are changing from helium to hydrogen plasmas, our proper subject of investigation.”