The first truly all-aluminum alloy ultrahigh vacuum system for an electron-positron accumulation ring is described. The ultimate pressure, the order of 10
-8 Pa, was obtained without any baking or discharge cleaning. For a time integrated beam current of 15 A.h, the pressure rise due to synchrotron radiation was 2×10
-8 Pa/mA and the maximun beam life time was about 2hours for 10mA. We have no problem essentially in the all-aluminum vacuum system. The present system satisfied conditions such as high performance, high reliability, impedance matching, simplicity, low wasted space between magnets, small size, low residual radioactivity and low cost.
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