The H-mode power threshold in hydrogen plasmas in DIII-D

In DIII-D, experiments have been performed in hydrogen plasmas to determine the requirement for hydrogen operation in ITER. The H-mode threshold power has been determined to increase with input torque for both hydrogen and deuterium plasmas with the H-mode power threshold for hydrogen plasmas being greater by approximately a factor of 2 at zero torque than in comparable deuterium plasmas. The threshold power for hydrogen discharges with full counter-current beam injection is roughly the same as the threshold power for deuterium discharges with co-current beam injection. The plasma geometry also influences the power threshold through the vertical distance between the X-point and the divertor surface.