Operation of RF-driven negative hydrogen ion source in China Spallation Neutron Source

The China Spallation Neutron Source started delivering neutron beams to users in March 2018. To upgrade the beam power to 500 kW and improve the performance of the ion source, an RF-driven negative hydrogen (H−) ion source is under development. The source has a silicon nitride ceramic plasma chamber surrounded by a 4.5-turn antenna. The plasma is ignited by a pulsed DC spark gap and then driven by a 2 MHz solid-state amplifier with a repetition rate of 25 Hz. The commissioning of the source started in January 2019. When uncesiated, it produced about 20 mA beam at an RF power of 32 kW and pulse width of 450 μs. This paper describes the configuration of the ion source, several peculiar technologies used in it, and the first negative hydrogen (H−) ion beam extraction.