Ultrahigh Vacuum Technology for Storage Rings

Present UHV technology permits producing pressures of 10-9 to 10-11 torr in the aperture-limited vacuum chambers of storage rings. Very disturbing pressure rises occur in electron storage rings from synchrotron light and in proton storage rings from ion bombardment. This has prompted the development of special cleaning and bakeout procedures on chambers before installation and in situ. In some cases, cleaning and baking alone are not sufficient and a pumping action distributed all along the pipes must be provided for. A controversy exists whether one should use, for future superconducting storage rings, a cold (4 K), cool (77 K) or warm (293 K) bore vacuum chamber. Experiments are in progress to supply the basic facts needed for taking decisions.