Synchrotron-radiation-induced heating effects in the PEP storage ring vacuum system

The advent of large high-energy storage rings has facilitated the need for more detailed analysis of synchrotron radiation interactions and related thermal effects. In the PEP storage ring, a maximum of 5 MW of synchrotron radiation with a critical energy of 44 keV will interact with 2200 m of vacuum hardware. A Monte Carlo based computer code, EGS, was employed to follow electromagnetic reactions of the synchrotron radiation through various computerized models of the vacuum system. The computer simulated structures with hundreds of discrete regions and varying materials. Results showed that typically 70% of the synchrotron power was absorbed in incident surfaces and 20% was scattered outside the vacuum vessel. The remaining power was deposited in varied vacuum components. Sensitive PEP ring components, particularly distributed ion pumps, were subsequently designed to minimize power absorption and to maximize cooling effects. Other thermal calculations were employed to design for minimal wall temperatures in areas of direct synchrotron radiation incidence.