DEVELOPMENT OF THE KEK VOLUME H- ION-SOURCE

Characteristics and performance of the recently developed volume H- ion source at KEK are described in this article. In particular, observation of the H- beam intensity enhancement by introducing a very small amount of cesium vapor is shown in detail. The extracted H- beam current of 20 mA was obtained in the cesium-mode operation. The measured 90% normalized beam emittance was about 1-pi-mm mrad for 12 mA beam, and emittance growth due to the space charge effect was observed when the beam intensity increased. We also made experiments on the cesium effect and found that the work function of the cesium-covered surface of the beam extracting plasma electrode might have an important role to enhance the H- beam intensity.