Development of ion beam sources with wide beam energy and current ranges

Using a neutral beam injection system with large electrodes for a nuclear fusion device, high currents of nitrogen ion (N+) beams with energies of 300 V are successfully extracted for plasma application. In an acceleration with a low energy of 300 V, a N+ beam current (∼9 mA/cm2) on the ampere order is achieved without the optimization of extraction aperture diameter, electrode thickness and the distance between the electrodes. Main beam elements are confirmed as N+ particles using a mass spectrometer. In this system, concave electrodes with an effective diameter of 345 mm are adopted to focus the beams. Therefore, we can obtain a high current density and high-flux ion beam at the focal point. In an acceleration with a high energy of ∼23 kV, a N+ beam with a current density of ∼456 mA/cm2 and a flux of ∼3.1x1022 m-2 s-1 is irradiated onto an aluminum material, then surface modification is confirmed. (author)