Study of the thermo-mechanical properties of a lead-stainless steel composite at 298 K and 77 K

Abstract ALLEGRO is a proposed FCC-ee general-purpose detector concept with a noble-liquid electromagnetic calorimeter (ECAL) as one of its central detectors. Noble-liquid calorimetry is a strong option for future particle physics experiments – for both, hadron and lepton colliders. Such an ECAL is composed of a sandwich of 1536 multi-layer read-out electrodes realised as PCBs and the same number of absorbers immersed in a liquified noble gas at cryogenic temperatures. The absorbers are made of metallic composites using lead as core and stainless steel as skin. The different thermal contraction coefficients of these materials as well as the resin used to glue them together, cause residual stresses in the layers. A careful study of this composite is needed to characterise its thermo-mechanical behaviour and to avoid high stresses at operating conditions. Theoretical and numerical studies have been conducted, along with strength and contraction tests, to determine the material’s yielding point and its thermal contraction between room temperature and 77 K.