Evaluation of the deflections in the radiator vessel of the ALICE RICH array using numerical methods

The RICH array in ALICE (A Large Ion Collider Experiment) at CERN-LHC is being designed following the basic criterion to optimize the detector performances in terms of Cherenkov angle resolution and the minimisation of the total material traversed by the incoming particles. Due to the physics requirements, low deformation of the liquid freon container is mandatory, therefore a careful engineering design to predict the deflection of the radiator structure when filled with freon is needed. The aim of this study is the design of the liquid freon container under different static load conditions since the RICH array is placed in a barrel frame structure of about 4 m radius and 8 m length. Because of its high stiffness and low weight, a honeycomb sandwich with NOMEX® core and carbon fiber skins is used for the vessel structure. Different solutions are analyzed using numerical techniques, based on Navier double series expansion and finite element method. They show good agreement and highlight the possibility of obtaining negligible stresses and strains.