Connection Cryostats for LHC Dispersion Suppressors

The lattice of the Large Hadron Collider (LHC) being built at CERN is based on 8 standard arcs of 2.5 km length. Each arc is bounded on either side by Dispersion Suppressors connected to the arc by connection cryostats providing 15m long drift spaces. As for a dipole magnet, the connection cryostat provides a continuity of beam and insulation vacuum, electrical powering, cryogenic circuits, thermal and radiation shielding. In total 16 modules will be constructed. The stringent functional specification has led to various design options. Among them, a light mechanical structure has been developed with a stiffness comparable to that of a dipole magnet, for alignment purpose. Thermal studies, including lambda front propagation, have been performed to ensure a cooling down time to 1.9 K within the time budget. A special cooling scheme around the beam tubes has been chosen to cope with heat loads produced during operation. We report on the general design of these modules and on the adopted manufacturing process which guarantees the tight alignment of the beam tubes once the module is installed in the machine. Special emphasis is given on thermo-mechanical analysis, lambda front propagation and on the beam-tube cooling scheme.