Ultra-light and stable composite structure to support and cool the ATLAS pixel detector barrel electronics modules

The design of an ultra light structure, the so-called "stave", to support and cool the sensitive elements of the Barrel Pixel detector, the innermost part of the ATLAS detector to be installed on the new Large Hadron Collider at CERN (Geneva), is presented. Very high- dimensional stability, minimization of the material and ability of operating 10 years in a high radiation environment are the key design requirements. The proposed solution consists of a combination of different carbon-based materials (impregnated carbon-carbon, ultra high modulus carbon fibre composites) coupled to a thin aluminum tube to form a very light support with an integrated cooling channel. Our design has proven to successfully fulfil the requirements. The extensive prototyping and testing program to fully qualify the design and release the production are discussed.