Contribution of local H- density to extracted H- beam current in a cesium seeded hydrogen plasma

Temporal behavior of H- beam current after photodetachment was measured by means of the irradiation of laser light inside the plasma near a plasma electrode in a hydrogen negative ion source. As the distance between the laser path and the extraction hole was increased, the change in H- beam current due to photodetachment decreased indicating a smaller contribution to the extracted beam by H- ions transported from the region deeper inside of the ion source. Addition of Cs into the discharge increased the extracted H- current, while the change in H- current due to photodetachment showed stronger dependence upon the distance between the laser path and the plasma electrode