R&D for the local support structure and cooling channel for the ATLAS PIXEL Detector Insertable B-Layer (IBL)

ABSTRACT: The scope of the present R&D is to develop an innovative support, with an integrated cooling and based on carbon composites, for the electronic sensors of the Silicon Pixel Tracker, to be installed into the ATLAS Experiment on the Large Hadron Collider at CERN. The inner layer of the detector is installed immediately outside the Beryllium beam pipe at a distance of 50 mm from the Interaction Point, where the high energy protons collide: the intense radiation field induce a radiation damage on the sensors so that a cooling system is necessary to remove the electrical power dissipated as heat, maintaining the sensor temperature sufficiently low. The task of the support system is to hold the detector modules in positions with high accuracy, minimizing the deformation induced by the cooling; this must be done with the lower possible mass because there are tight requirements in terms of material budget. An evaporative boiling system to remove the power dissipated by the sensors is incorporated in the support: thermal contact is made through a very conductive light carbon foam to maintain the sensor temperature sufficiently low, to limit the leakage currents and so the thermal run-away. The coolant should be CO2, with a cooling pipe design pressure of 10 MPa. The number of pipes could be 1 or 2 and the pipe material should be carbon fiber or titanium. The structural strength of the 800 mm long support stave is given fro m a carbon fiber laminate omega shaped. The design is based on thermal/mechanical/thermo-structural analysis of assemblies made of carbon fiber composites. One R&D key element is thr production of the Carbon Fiber or Titanium pipe and of the relative joints versus the external connecting piping, having suitable mechanical and tightness properties.