Abstract
Based on experiences in the precedent stain-less steel case, a possibility of employing copper-alloy and aluminum-alloy Matsumoto-Ohtsuka (MO)-type flanges in a vacuum beam pipes for a particle accelerator is experimentally studied. They can mitigate the heating problems found in the case of stainless-steel flanges under high-intensity beams, and also simplify the manufacturing procedure of beam pipes. Copper-alloy flanges show a comparable vacuum sealing property to the stainless-steel one, and several beam pipes with the copper-alloy flange has been successfully installed in the KEKB B-factory positron ring. The R&D on aluminum-alloy flanges has just started, and a promising result is obtained. Any coatings or treatments to improve the hardness of sealing part can be omitted if duralumin-series aluminum alloys are used. However, further detailed investigations are required about the hardness and stiffness properties of the gasket and flange materials before applying the flanges to the real machine.
