THE TESLA CRYOGENIC ACCELERATOR MODULES

The Tera-eV Energy Superconducting Linear Accelerator (TESLA), a 32 km long superconducting linear electron/positron collider of 500 GeV (upgradeable to 800 GeV) centre of mass energy, presently in the planning phase at DESY, will consist of about 21000 superconducting RF 9-cell cavities of pure Niobium. Each cavity of about 1 m length has to be cooled in a 2.0 K helium bath and operated at 1.3 GHz with 5 Hz beam repetition rate. The cavities, equipped with their individual helium vessels made from titanium, RF input couplers , tuners and magnetic shielding, will be assembled in groups of 12 in about 16 m long cryostats (cryomodules) with thermal radiation shielding at 5-8 K and 40-80 K. Part of the cryomodules will also be equipped with superconducting quadrupoles and steering coils. About 10% of the cryomodules will contain cryogenic valves and instrumentation required for cooling purposes. The paper presents design, construction and assembly details of the cryomodules, which are based on the experience with somewhat shorter cryomodules, already in use at the TESLA Test Facility (TTF) at DESY.