Design concepts of modern accelerator vacuum systems-prediction vs. experimental data

Design parameters for accelerator vacuum systems are studied with reference to the requirements which appear in modern strong-focusing machines. The two major problems considered are restrictions in both pumpdown time and system base pressure created by trends toward very small apertures. Basic kinetic equations are used in a method of estimating performance. Assuming a time-dependent outgassing rate from vacuum chamber walls, equations are offered for predicting progression of evacuation and base pressure distribution throughout the system. Results from small-scale experimental systems are reported and compared with predicted performance. Influence of various pumping systems on prediction is discussed, and design recommendations are offered.