Experimental investigation of the Cs behavior in the cesiated H^- ion source during high power long beam operation

The behavior of the Cesium (Cs) in Cs-seeded negative ion sources has been investigated experimentally under the beam accelerations of up to 0.5 MeV. The pulse length was extended to 100 s to catch the precise variations in the Cs D2 emission, discharge power, negative ion current, and temperatures in the ion source. The variations of the negative ions were estimated by the beam current and the heat loads in the accelerator. This experiment shows that the buildup of temperature in the chamber walls lead to the evaporation of deposited Cs to enter the plasma region and influenced H^- ion production. The H^- ion beams were stably sustained by reducing the temperature rise of the chamber wall below 50 °C. A stable long pulse beam could be achieved through the temperature control of the surfaces inside the source chamber walls.