Thermohydraulic simulation of quenches and quench recovery for the HL-LHC IT String test bench at CERN

In the framework of the High Luminosity LHC (HL-LHC) project, a new test system - the Inner Triplet (IT) magnets String - for the characterization and validation of the collective behaviour of a 60 m long string of magnets is being built in the SM18 cryogenic test facility at CERN. Among the main objectives of the IT String is the assessment of the magnet performance during the resistive transition from the superconducting to the normal state (quench) when energies up to 39.1 MJ are released into the magnet cold mass and into the helium. In this paper we present the thermohydraulic study performed to design the quench recovery system of the IT String, which limits the pressure rise in the magnets during a quench and ensures the recovery of the operating conditions within the required timeframe. As a new design method, a 1-D thermohydraulic model of the quench relief system has been created using the EcosimPro software with the CRYOLIB library developed at CERN.