Positive ion extraction from plasma source and its application in fusion research

Neutral Beam Injection (NBI) is well established technique for heating tokamak plasma and is used in all fusion research programs 1–2]. In our Steady state Superconducting Tokamak (SST) machine 3], neutral hydrogen beam power of 0.5 MW at 30 kV is required to raise plasma ion temperature of ∼1 keV. Future upgrade of the SST will require 1.7 MW of H^o at 55 kV. To fulfill this requirement, an ion extractor system (heart of any NBI system) has been designed to extract 35A H⁺ beam current at 30 kV and of 90 A at 55 kV respectively 4]. In this paper, we have described the physics and ion beam optics study for an ion extraction system suitable for above mentioned long dynamic range of acceleration voltage. The ion beam optics simulation result is used as an input to the engineering design. After fabrication, its performance test has been done. The experimental results are in very good agreement with beam optics simulation.