New Techniques for the Petra Vacuum System

New techniques have been developed at DESY to meet the PETRA requirements for a "smooth" vacuum system with low rf parasitic mode losses and low fabrication costs. The PETRA vacuum chambers are being made of an extruded aluminum profile with a four-channel cross-section to accept respectively the beam, the integrated sputter-ion pumps, the water-cooling and the bake-out elements. Spark-erosion technique is being used to connect the beam and pump channels with 1000 slots per chamber. Two novel techniques have been developed to join aluminum to stainless steel by "TIG" or friction welding. The chambers will be connected by welding two bellow membranes with a special welding machine. The "smooth" transition is achieved by using a spring contact ring between the sliding chamber ends. Integrated sputter-ion pumps with two different cell diameters provide the needed pumping speed over the whole PETRA operating range. The anodes of the integrated pumps will be used to clean the vacuum system in-situ by Argon glow discharge.