Repeatable 400-second longpulse plasma discharges achieved on HT-7 tokamak

After achieving 300-second-long high temperature plasma on HT-7 tokamak, scientists and engineers at the Institute of Plasma Physics have analyzed various factors that impeded longer duration of plasma discharges, conducted indepth investigation into a number of key physical and technical issues, applied a few important techniques and upgraded the device. The main technical improvements include the introduction of the thermal deposition materials and technologies developed for EAST tokamak to rebuild HT-7 limiter, improvement of the whole electro-magnetic diagnostic system, development of the configuration reconstruction technique in the case of iron core, and the technique to control plasma magnetic flux by adjusting the power of the low hybrid wave and the real-time monitoring and control technique for the limiter temperature. Through the adoption of these new techniques and the upgrade of the device systems, repeatable and stable 400 second long-pulse plasma discharges were successfully achieved on HT-7, with the plasma current above 60ka, electron density ranging 0.6~1×1019/ m3, central electron temperature over 10,000,000 degrees. This is known as the longest duration high temperature plasma discharge in the world.