Due to its unusual geometry and gas load, the SPEAR vacuum system incorporates several unique design features. The system consists of an aluminum chamber in the form of a 200-ft-diam ring which must achieve a pressure in the 10−9 Torr range with a large gas load due to synchrotron-radiation-induced desorption. Since the system is conductance limited, it was necessary to develop distributed sputter-ion pumps located within the chamber proper. A large number of aluminum-stainless-steel interfaces required the development and testing of various flange arrangements which would withstand a bakeout to 200 °C.