New aspects on the design of the vacuum system for the future synchrotron light sources

摘要

In vacuum systems of proton or electron storage rings, the ultimate pressure without beam should reach the 10↑(-11)mbar range. It was believed that long lifetimes due to gas density at high stored currents (＞250mA@2/2.5 GeV) need pumping speed of thousands of litres per second and the vacuum components must be pre-baked before mounting under high vacuum and high temperature. Recent experimental results from existing storage rings confirmed that the desorption yield from the vacuum degassed and non degassed stainless steel is the same. The wall conditioning seems to be very rapid and even a non bake-out start up can be considered. New approach for vacuum system design based on three years of experience with Elettra vacuum system !presented. In this approach the dominant vacuum system parameter is not the pumping speed but the ultimate, pressure reachable by installed pumps. This condition was verified, switching off more than 60% of installed pumps during machine operation (200 mA@2 GeV) without any significant lifetime decrease. #1997, Elsevier Science Ltd. All rights reserved