Reliability-based dynamical design of a singular structure for high energy physics experiments

The present work presents a comprehensive design and dynamic calculation of singular metallic structures, part of the Neutrino Experiment NEXT. The experiment uses an electroluminescent TPC chamber, a high-pressure 136Xe gas vessel enclosing the detector. A lead-block “castle” or containing box shields this vessel against external γ-rays from all directions; in spite of its heavy weight, the castle must be regularly open for the detector maintenance. Since the structures will be constructed at a middle-level seismic localization (Laboratorio Subterráneo Canfranc, Spain), the earthquake hazard must be taken into account. Vessel and castle are supported by a rigid frame, which must satisfy two requirements: (i) the Spanish seismic standard, (ii) for equipment protection, the detector maximum horizontal acceleration must be <1 [m/s2]. This frame rests on special base isolators to decrease horizontal accelerations in case of an earthquake. Three dynamical calculations are conducted: (i) a response spectrum analysis to comply with the standard, (ii) five time-history analyses to calculate tolerances and, (iii) a reliability-based approach using 1000 time-history responses to ensure satisfaction of the operating requirements. The final outcome is the design of a singular structure optimized for the NEXT experiment with a probability of failure against any standard earthquake of only 0.125%.