Operating the SNS RF H- Ion Source with a 10% Duty Factor

The SNS (Spallation Neutron Source) (radiofrequency) RF-driven, Hion source injects ~50 mA of Hbeam into the SNS accelerator at 60 Hz with a 6% duty factor. It injects up to 7 A·hrs of Hions during its ~14week service cycles, which is an unprecedented lifetime for small-emittance, high-current pulsed Hion sources. The SNS source also features unprecedented low cesium consumption and can be installed and started up in <10 h. Presently, the LANSCE (Los Alamos Neutron Science CEnter) accelerator complex in Los Alamos is fed by a filament-driven, biased converter-type Hsource that operates with a high plasma duty factor of 10%. It needs to be replaced every 4 weeks with a ~4 day startup phase. The measured negative beam current of 16-18 mA falls below the desired 21 mA acceptance of LANSCE’s accelerator especially since the beam contains several mA of electrons. LANSCE and SNS are exploring the possibility of using the SNS RF Hsource at LANSCE to increase the Hbeam current and the ion source lifetime while decreasing the startup time. For this purpose, the SNS Hsource has been tested at a 10% duty factor by operating it at 120 Hz with 840 μs plasma pulses generated with ~30 kW of 2 MHz RF power, and extracting ~25 mA around-theclock for 28 days. This, and additional tests and other considerations are discussed in this paper.