Characteristics of cesium-free negative hydrogen/deuterium ion source by sheet plasma

Highlights: • We have designed the magnetized-sheet plasma. • The negative ions produce by volume production without Cs seeding. • The negative hydrogen /deuterium ions are successfully extracted. • This study clarified the basic characteristics of the developed system. -- Abstract: The use of negative ion sources without Cs seeding is desired in neutral beam injectors of fusion experiments. We have designed a magnetized-sheet plasma that produces negative ions by volume production without Cs seeding. The developed system was experimentally tested on steady-state hydrogen and deuterium plasmas. The negative hydrogen ion beam was extracted by a two-grid extraction system located at the periphery of the sheet plasma. The negative hydrogen/deuterium ions were successfully extracted from the sheet plasma. The current densities of the ion beams increased with increasing discharge current. At an extraction voltage of 7 kV and a discharge current of 80 A, the approximate current densities of the negative hydrogen and deuterium ion beams were 3.8 and 1.2 mA/cm², respectively.