Recent operation status of Japan Proton Accelerator Research Complex H- ion source.

A cesium-free H(-) ion source driven with a LaB(6) filament is being operated at the Japan Proton Accelerator Research Complex for approximately three years without any serious trouble. In the beam commissioning or supply runs, the ion source has been operated in two different modes such as low current mode of 5 mA and high current mode of 30 mA. The total interruption time during the runs due to the ion source failure is approximately 50 h, which correspond to the ion source availability of 99%. After a long-term operation, the surface of the filament and the plasma electrode become discolored with dark partially. The result of surface analysis with field emission scanning electron microscope showed that most of the dark material is formed with boron. At the beam test performed in the interval of the run, we demonstrated that the H(-) current increased by miniaturizing the LaB(6) filament.