Quench Protection of the HL-LHC Hollow Electron Lens Superconducting Solenoid Magnets

The High-Luminosity LHC (HL-LHC) project is an upgrade of the Large Hadron Collider (LHC) and comprises the installation of two Hollow Electron Lens (HEL) systems, each acting on one beam on both sides of LHC Point 4. The systems aim for a controlled depletion of hadron beam tails and an enhanced hadron beam halo collimation. Each HEL unit contains 22 circuits made up of solenoid, saddle coils and canted cosine theta corrector magnets. The largest magnet is a 1.6 m long solenoid, with a 180 mm bore diameter and central field of 5 T at 300 A and 4.5 K. This contribution focuses on the powering and protection strategy of the solenoid magnet circuits. The circuits are protected by active quench detection and a timely switch-off of the power converter. For the circuit with the largest stored energy, a study is performed on the efficiency of an energy extraction system. The quench simulations performed using the STEAM-LEDET code are combined with uncertainty quantification methods available in the DAKOTA software. Quench simulation input parameters related to the superconducting wire, magnet, circuit, and detection have been parametrized and randomly varied to calculate statistics of key output parameters. These are compared to the allowed limits, namely 500 V maximum peak voltage-to-ground and 120 K maximum coil temperature.