The vacuum system of KEKB

摘要

For the KEK B-factory, two rings with a circumference of 3016 in, mainly made of copper, were constructed. A gap between the flanges is filled using Helicoflex as a vacuum seat. The contact force of an RF finger in a bellows is assured by using a spring finger. Pumping slots are backed by crossing bars to prevent the penetration of beam-induced fields. To obtain a pressure of 10(-9) Torr with the beam when the photo-desorption coefficient reaches 10(-6), the design of pump layout is aimed to realize 100 iota s(-1) m(-1). NEG strips are used as the main pump. Chemical polishing is applied to clean the extruded surface of a copper chamber. Almost all chambers were baked before installation. Only ion pumps were baked in situ. The photo-desorption coefficient at the start of commissioning was slightly higher than expected, but a decrease of the coefficient is as expected on the whole. At high currents, some bellows were found to be warmed by the TE mode of beam induced fields. The effect of the electron cloud became evident, especially in the LER. Direct damage by the beam is seen at the surface of the movable mask. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 12]