Experience of baffle cooling on 36 inches diffusion pump in the main vac system of VEC

Cyclotron Resonator and 'D' tanks are evacuated by two nos. 89 cm diffusion pumps operating in parallel. Cooled chevron baffles are placed on the top of diffusion pumps to prevent back-streaming and back-migration of DP oil into the cyclotron chamber. At present baffles are cooled by 2 stage cascade system freon units which attain a temp of -40deg in the baffles. It is thought that lower temp in the baffle will reduce oil migration. Passing of liquid nitrogen through the baffles was ruled out for technical and economical reasons. Alternatively, cryocoolers attaining temp of -100degC are being explored for the job. (author). 3 figs