Alignment of the Superconducting Cryostat for the Tesla Test Facility

The cryostat is the principal building block of the proposed TESLA- superconducting linac. It contains 8 superconducting RF cavities made from solid pure niobium and a quadrupole package. The cryostat includes two aluminum shields of 4.5 and 70 K with multilayer insulation on the outside. The helium distribution system needed to operate the superconducting cavities at 2 K and the magnets at 4.5 K is also integrated into the cryostat. The two phase line transfers helium to the cavities, the gas return line transports gas from the cavities to the refrigeration plant. This line is connected to the cavity helium vessels via a helium bath at the end of the module. The 4.5 K forward and return lines cool the quadrupole package, the radiation shield and the 4.5 K intercept on the input coupler. The 70 K lines have the corresponding effect on the outer radiation shield and the 70 K intercept of the coupler. The cryostat outer vacuum vessel is constructed of carbon steel and is evacuated to a pressure of less than 10-6 mbar during operation. In the Tesla Test Facility TTF it is connected by sliding sleeves to a feedcap which provides the link to the cryogenic supply at the upstream end of the prototype module. At the downstream end it is closed off by an endcap which seales off the vacuum space and turns around all the cryogenic flows [1]. Wires and cables are brought out at the module itself using flanges equipped with vacuum tight connectors. Figure 1 shows a cross section of the cryostat. He gas return pipe (support girder) 4.5 Kreturn 70 Kreturn input coupler vacuumvesse