The operation of the KEKB accelerator at KEK started on December 1998 after
about 4 years' construction. More than 2000 vacuum chambers and their atta
chments were installed progressing through some stages in last 2 years. Eac
h stage was set with specified procedure and under careful quality control.
The average base pressure in the order of 10(-8) Pa just before the commis
sioning, and the following decrease of photon stimulated gas desorption pro
ved the validity of our procedures. (C) 2001 Elsevier Science B.V. All righ