Powering via Cooling Pipes: an Optimized Design for an SLHC Silicon Tracker

Silicon trackers at the SLHC will suffer high radiation damage from particles produced during the collisions, which leads to high leakage currents. Reducing these currents in the sensors requires efficient cooling to -30 C. The large heat of evaporation of CO2 and the low viscosity allows for a two-phase cooling system with thin and long cooling pipes, because the small flow of liquid needed leads to negligible temperature drops. In order to reduce the material budget a system is proposed in which a large scale tracker requiring ca. 50 kW of power is powered via 1-2 mm diameter aluminum cooling pipes with a length of several m. These long cooling pipes allow to have all service connections outside the tracking volume, thus reducing the material budget significantly. The whole system is designed to have negligible thermal stresses. A CO2 blow system has been designed and first tests show the feasibility of a barrel detector with long ladders and disks at small radii leading to an optimized design with respect to material budget and simplicity in construction.