Towards Reliable Acceleration of High-energy and High-intensity Electron Beams

KEK electron linac was upgraded to 8 GeV for the KEK B-Factory (KEKB) project. During the commissioning of the upgraded linac, even continuing SOR ring injections, we had achieved a primary electron beam with 10-nC (6.24 x 10^10) per bunch up to 3.7-GeV for positron generation. This could be classified as one of the brightest S-band linac's. Since the KEKB rings were completed in December 1998, those 3.5-GeV position and 8-GeV electron beams have been injected with an excellent performance. Moreover, we have succeeded in switching among the high-intensity beams for KEKB and beams for two SOR rings with sufficient reproducibility. After the commissioning of the KEKB ring started, we have launched a project to stabilize the intensity and quality of the high-current beams furthermore, and have accomplished it investigating every conceivable aspect.