Low-induced radioactivity ultrahigh vacuum system using aluminum alloy

In the High Energy Physics Laboratory in Tsukuba, the development of an ultrahigh vacuum system made of aluminum was successfully achieved for the first time in the world, and at present, the TRISTAN ring is under construction. The discovery and verification that aluminum and its alloys are very advantageous for reducing radioactivity exposure became the opportunity to begin, and the research has been advanced, as the result, also the rate of released gas was able to be improved as compared with conventional stainless steel. The application to nuclear fusion equipment, semiconductor production facility such as molecular beam epitaxy and analysis equipment as well as accelerators is promoted. The induced radioactivity of five kinds of metallic sheets was compared, and the change of the material for the vacuum system of particle accelerators to aluminum alloy was planned. The newly developed ultrahigh vacuum system made of aluminum alloys is described, and its application to the particle accelerator TRISTAN is explained. In the application to nuclear fusion experimental apparatus, the use of Al-Li-Mg alloy may resolve the problems. The findings obtained at the Laboratory are shown. (Kako, I.)