Development and design of the negative-ion-based NBI for JT-60 Super Advanced

A large negative ion source with an ion extraction area of 45 cm x110cm has been developed to produce 500 keV, 22 A D ion beams required for JT-60 Super Advanced. To realize the JT-60SA negative ion source, the JT-60 negative ion source has been modified and tested on the negative-ion-based neutral beam injector on JT-60U. The significant effort has been made for the high-energy beam production and the long pulse injection. By improving voltage holding capability of the negative ion source, a 500 keV H ion beam has been successfully produced at the beam current of 3 A through 20% of the total ion extraction area. This is the first demonstration of a high-energy negative ion acceleration of more than one-ampere to the beam energy of 500 keV in the world. A long pulse injection of 30s has been achieved at an injection D 0 power of 3 MW by reducing the power loading of the acceleration grids in the negative ion source. The injection energy, defined as the product of the injection time and power, reaches 80 MJ of the limitation of the heating time allowed on JT-60U. This is the world record of the injection energy from one injector.