Development of Cs-Free Negative-Ion Source by Sheet Plasma

抄録

The use of cesium leads complicates ion source operation and requires regular maintenance for continuous operation. The development of a negative-ion source without Cs seeding is desired in neutral beam injectors. A magnetized-sheet plasma producing negative ions using volume production without Cs seeding was designed. The experiment was performed by a TPDsheet-U and tested using steady-state hydrogen plasma. Two different types of grid structures were used in the experiment to extract the negative-ion beam: single- and multi-aperture grids. The multi-aperture grids have been developed to achieve more beam current. The negative hydrogen ions were successfully extracted from the sheet plasma using both single- and multi-aperture grids. The current densities of the ion beams increased with increasing discharge current and extraction voltage. At an extraction voltage of 9.5 kV and a discharge current of 80 A, the approximate current density of the negative hydrogen ion beam was 8.4 mA/cm² for the case of single-aperture grids. At an extraction voltage of 9.5 kV and a discharge current of 50 A, the approximate current density of the negative hydrogen ion beam was 23 mA for the case of multi-aperture grids.