Mastering nuclear fusion, which is an abundant, safe, and environmentally competitive energy, is a great challenge for humanity. Tokamak represents one of the most promising paths toward controlled fusion. Obtaining a high-performance, steady-state, and long-pulse plasma regime remains a critical issue. Recently, a big breakthrough in steady-state operation was made on the Experimental Advanced Superconducting Tokamak (EAST). A steady-state plasma with a world-record pulse length of 1056 s was obtained, where the density and the divertor peak heat flux were well controlled, with no core impurity accumulation, and a new high-confinement and self-organizing regime (Super I-mode = I-mode + e-ITB) was discovered and demonstrated. These achievements contribute to the integration of fusion plasma technology and physics, which is essential to operate next-step devices.

The experimental advanced superconducting tokamak (EAST) is one of the fully superconducting tokamaks. A high-power neutral beam injector (NBI) system consisting of two injectors (EAST-NBI) was employed on EAST for plasma heating and current driving. The designed deuterium beam energy is 50-80 keV, beam power is 2-4 MW, and the beam duration is 10-100 s. Each beamline is equipped with two hot cathode ion sources and can be operated individually. In order to support the planned physics research on EAST, the NBI-2 was shifted from port F to port D, and at the same time, its injection direction was changed from counter-injection to co-injection. Furthermore, the high power ion source was optimized with better feedback control for stable long pulse beam, and a new technology of beam re-turn on was also developed and applied aiming at long pulse beam injection. Details of the NBI status will be presented in this article.

A research project of the China Fusion Engineering Test Reactor (CFETR) Negative ion-based Neutral Beam Injection (NNBI) prototype has been started in China. The objectives of the CFETR NNBI prototype are to produce a negative hydrogen ion beam of >20 A up to 400 keV for 3600 s and to attain a neutralization efficiency of >50%. In order to identify and optimize the design of the negative ion accelerator, a self-consistent model has been developed to consider all key physics and engineering issues (electric and magnetic fields, background gas flow, beam optics, beam-gas interaction, secondary particle trajectories, power deposition on grids, heat removal design, and mounting pattern). This paper presents the primary results by applying the self-consistent model to the current design of the 400 keV H⁻ accelerator of the CFETR NNBI prototype.