Upgrade and experimental results of radio frequency ion source for neutral beam injector

Highlights: • The RF ion source was developed in ASIPP for the first time. • The gas control was employed for the initial plasma production successfully. • The RF power was controlled for the stable plasma generation with high power. • Long pulse operation was tested and analyzed with 400 s. - Abstract: A radio frequency (RF) ion source was designed and developed for neutral beam injector in Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). Recently, the RF ion source was upgraded with new RF power generator (50 kW with frequency of 1 MHz), a new matching unit and the faraday shield with water cooling. Two new methods were used for the ion source tests on the test bed. The high pressure was used for the ignition of plasma and change to low pressure of 0.3 Pa to maintain the plasma. The RF plasma can be generated without the start filament successfully. In order to avoid the plasma oscillation with high power, the RF power was set to increase with two stages without change the matching unit. High power of 46 kW with pulse length of 22 s was achieved on the test bed and the plasma duration can be extended too.