s _- * __ !!B EISEVIER Nuclear Instruments and Methods in Physics Research A 371 ( 1996) 271-274 NUCLEAR INSTRUMENTS 6 METHODS IN PHYSICS =!zttT” Evaluation of the deflections in the radiator vessel of the ALICE RICH array using numerical methods G. Demelio”, L.M. GalantucciaTb, A. GrimaldiaTb, E. Nappib3*, F. Posa”“, V. Valentinob zyxwvutsrqpo “Polirecnico di Bari, Bari, Ita!\ “INFN. Se:. Bari. Bari. Italy zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONM Abstract 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 tinite element method. They show good agreement and highlight the possibility of obtaining negligible stresses and strains. 1. Introduction The RICH array in ALICE is being designed following the basic criterion to optimize the detector performances in terms of the Cherenkov angle resolution [I]. A modular construction is envisaged with sixty elements arranged in five annuli of approximately 4 m radius and 8 m length; each annular surface is tilted in such a way that the average direction of incoming particles is almost perpen- dicular (Fig. I ). The RICH performance depends strongly on the liquid C,F,, thickness, transparency and its long term stability. therefore emphasis has been put on the definition of the radiator vessel mechanical design. Dimensions, weight, density and chemical resistance to freon C,F,, are the main constrains considered in design- ing the structure. The radiator vessel under study can be represented with a base sandwich panel, 1700 mm long and 1700 mm wide, presenting four ribs intersecting half way along the innerplane and four more ribs along the outer edges (Fig. 2). Inside the sandwich, in corre- spondence with the upper ribs, is placed a carbon fiber beam gridwork with a box section having the width of the upper beam, height of sandwich core and 2 mm thickness. In this way nine independent volumes 500 mm long, 500 * Corresponding author. Fig. I. ALICE RICH array isometric view. mm wide and 10 mm deep are obtained in which the liquid C,F,, is circulated. These volumes are closed to the opposite side of the base panel with nine windows of pure fused silica glass of 500 X 500 mm’ tightened to the rest of the structure by an additional frame (Fig. 3). 0168.9002/96/$15.00 0 1996 Elsevier Science BY. All rights reserved SSDI 016%9002(95)01172-2 VII. DETECTOR ENGINEERING