Complete overlapping of the electron and positron bunches at colliding point can be attained by using the strong time-depending electromagnetic RF field in the superconducting crab cavity. Commissioning of the crab cavities started in February 2007 at KEKB. Effective head-on collision of electron and positron has been achieved successfully. After introduction of crab crossing and crab cavity, the structure and the fabrication of the KEKB superconducting crab cavity are discussed.
A kenaf fiber-ice composite system can be used as a substitute for glass-fiber-reinforced plastics (GFRP). At the present time, electrical insulating systems at cryogenic temperature mainly use GFRP. However, GFRP dose not decompose naturally. A large negative environmental impact of GFRP has been pointed out as a problem to be solved. We have been suggesting the application of a natural fiber-ice composite system as an electrical insulating system in the cryogenic region. Kenaf is candidate of the natural material that has a low negative environmental impact. We pay attention to kenaf because it decomposes naturally and is characterized by its excellent elasticity and water absorption properties. In this study, we report the AC electrical breakdown strength (Fb) of a kenaf pulp-ice composite system is almost the same as that of GFRP. We consider that a kenaf fiber-ice composite system is promising as a substitute for the GFRP in electrical insulating systems used in the cryogenic region.