Conceptual design of a beam source for negative neutral beam injector of CRAFT facility

Abstract

The Comprehensive Research Facility for Fusion Technology (CRAFT) is a large scientific device that is preferentially deployed in China's "Thirteenth Five-Year Plan" for the construction of major national science and technology infrastructures. A beam source of negative neutral beam injector (NNBI) is required for the CRAFT device with the beam energy of 400 keV, neutral beam power of 2 MW, and beam duration of 100 s. The beam source is the key component of NNBI system. A radio frequency (RF) based negative beam source was designed for the CRAFT NNBI system. It contains a large plasma generator and a negative ion accelerator. The plasma generator contains a large expansion chamber and four RF drivers which arrange in a vertical column (1 × 4). The accelerator has a similar design to ITER. Consider the 400 keV beam energy, the accelerator was designed with four layers of electrodes, which are plasma grid, extraction grid, acceleration grid, and ground grid. The detailed structures of negative beam source were designed initially with the RF plasma generator and the negative ion accelerator.