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.

An RF-driven negative-ion source development program has been started at ASIPP-Hefei with a small test equipment, Hefei utility negative ion test equipment with RF source (HUNTER). It is devoted to some crucial issues of the RF-driven negative-ion source, such as the improvement of RF efficiency, the enhancement of the extracted negative-ion current density, and the promotion of the beam qualities. In the initial stage, the HUNTER negative-ion source conservatively adopted a similar structure of the ITER prototype source developed at IPP, Garching. It consists of single or double RF driver on the back side of a plasma expansion chamber, and a negative ion accelerator which is able to extract 120 beamlets up to 60 kV for 10 s. In the first phase operation of the HUNTER-ion source, a low-pressure (0.3 Pa) plasma has been successfully achieved by coupling 46-kW RF input power and different plasma parameters have been measured by using Langmuir probes and optical emission spectroscopy. Besides the negative-ion source, the HUNTER comprises the vacuum vessel, the special cooling system, the power supply system, and the source plasma and beam diagnostic system are also ready for the next phase operation of hydrogen negative ion beam extraction.

The Comprehensive Research Facility for Fusion Technology (CRAFT) is a large scientific facility that is preferentially deployed for the construction of major national science and technology infrastructures. A negative beam source based neutral beam injector (NNBI) with beam energy of 200–400 keV, beam power of 2 MW and beam duration of 100 s is one of the devices. A giant radio frequency (RF) based negative beam source was designed for the CRAFT NNBI system. In order to understand the physics and pre-study the engineering problems for RF negative beams source, several beam sources with different scales will be designed and tested. According to the R&D schedule, a negative beam source with a single driver was designed, developed and tested first. The single driver beam source is a quarter of the size of the full size negative beam source. It contains an RF driver, an expansion chamber and a negative ion accelerator with three electrodes, which are a plasma grid (PG), extraction grid (EG) and ground grid (GG). To enhance the negative ion production, Cesium is injected into the plasma chamber and a magnetic filter filed is produced by current flow through the PG to decrease the electron temperature. The negative beam source was tested on the test facility after assembly, including RF plasma generation, negative ion production, extraction and acceleration. The characteristic of plasma discharge, beam extraction and acceleration was studied without and with Cs injection. The long pulse of 105 seconds negative ion beam was achieved successfully. The extracted negative ion current is 4 A and the ratio of electron and negative ion is around 0.8. It lays a good foundation for the R&D of negative ion source with a multi-driver for the CRAFT NNBI system. The details of the design and experimental results of beam source was shown in this paper.