99.99% Al/6063 alloy coextruded cryogenic beam tube

A beam tube composed of 6063 alloy aluminum with a coextruded inner surface of 99.99% pure aluminum is proposed for the Superconducting Super Collider (SSC). It has higher electric conductivity than oxygen‐free pure copper at liquid‐helium temperature. Thermal desorption rate is ∼10−12 Pa l/s cm2 after 150 °C 24‐h baking. Dynamic gas desorption by synchrotron radiation from the inner surface at liquid‐helium temperature was measured with and without magnetic field. Magnetic field reduces the pressure rise by synchrotron radiation by one order of magnitude at liquid‐helium temperature. If a pure Al clad beam tube is accepted for SSC vacuum system, vacuum components of aluminum alloy which can be operated at liquid‐helium temperature are needed. Dynamic bellows, nonmagnetic feedthroughs, an all metal gate valve, a compact turbomolecular pump, an automatic welding machine, and a new type of pressure monitor along the ring have been developed.