Neutral beams at ROBIN with electrostatic ion separator

Abstract The RF Operated Beam source in India for Negative ions (ROBIN), a single-driver RF-based negative hydrogen ion (H - ) source test bed located at the Institute for Plasma Research, Gandhinagar, has been upgraded to enable neutral beam operations. It is a 1/8th size International Thermonuclear Experimental Reactor (ITER) reference design source. The upgrade includes beamline components, i.e. the gas neutralizer and the electrostatic residual ion dump (ERID). Operations have established the functionality and performance of these beamline components. The functionality of the ERID system is crucial because it utilizes an electric field to separate ions from neutral particles. This approach has been implemented for the first time in a neutral beam setup. However, it is important to note that the experiments were conducted with limited pumping capabilities, which differ significantly from those relevant to ITER neutral beam operations. This aspect is of special interest considering its use in the ITER heating and diagnostic neutral beam lines. Neutral beam experiments have been performed at low energy (around 10 keV), considering the available power supply rating of the ERID (−10 kV, 400 mA) for effective ion filtration purposes. The paper discusses these in light of the variation in neutralization efficiencies and ion beam currents dumped on the ERID as a function of variation in gas target thickness in the neutralizer cell and ERID voltages. Estimates related to neutralization and re-ionization have also been discussed. This experiment lays the foundation for the experimental learning important for ITER-diagnostic neutral beam-like operations on the Indian test facility.