PRESSURE DISTRIBUTION ANALYSIS OF THE KEK 2.5-GEV LINAC

Since the vacuum system of a linac comprises many conduit pipes (such as accelerator columns, waveguides and pump ducts) it is a multiply co nnected network. In such a network having n nodes, by introducing an n x n Green-function matrix determined by the network geometry, the pre ssure (p(i)) at the ith node can be expressed as (p(i)) = [G(ij)](Q(j) ), where (Q(j)) is the gas load. This type of analysis was applied to a KEK 2.5-GeV linac with 14 nodes, 19 branches and 2 pumps within the unit. The results show that the outgassing rate of the accelerator col umns made of oxygen-free copper decreases from approximately 10(-10) t o approximately 10(-11) torr / cm-2 s-1 after high-power conditioning.