Description
At the Korea Atomic Energy Research Institute, a novel Two Region Arc Plasma (TRAP) ion source is under development for negative hydrogen neutral beam injection (NBI) systems in fusion applications. A key advantage of this design is its ability to confine primary electrons emitted from the filament exclusively within the driver region, thereby eliminating the need for external filter magnets. In this configuration, the ratio of primary electrons to low-energy electrons in the driver and extraction regions can be precisely controlled by adjusting discharge parameters such as filament position, filament current, arc voltage, and gas pressure. This parameter tuning creates optimal conditions for negative ion production, especially within the extraction region. This study systematically investigates the effect of these parameters on negative ion generation. A diagnostic system, based on laser-induced photo-detachment combined with Langmuir probe measurements, was developed to evaluate the negative ion density. Experimental results demonstrate that, with optimized discharge conditions, a high density of negative ions can be achieved in the extraction region without relying on an external magnetic filter. This presentation will detail the diagnostic approach and discuss comprehensive experimental results
