The possibility of employing copper-alloy Matsumoto-Ohtsuka-type flanges in a vacuum beam pipes with complicated apertures for a particle accelerator is experimentally studied. Copper-alloy flanges can mitigate the heating problems arising as a result of high-intensity beams more efficiently than stainless-steel flanges. Baking of beam pipes up to a temperature of 200 degrees C was acceptable with copper-alloy flanges. Moreover, direct electron-beam welding to a copper beam pipe became available, which made the manufacturing easy. In this study, several beam pipes with copper-alloy flanges were installed in the KEKB B-factory positron ring, and the performance was investigated using the high-intensity beams. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3237149]