Impact of high-intensity LHC beam operation on warm vacuum modules

During the third run of the Large Hadron Collider in 2023, which had the highest intensity bunch population compared to previous runs, a beam dump incident with operational delays occurred due to increased losses attributed to pressure spikes within a warm vacuum sector. Subsequent inspections revealed localized annealing and plasticization of the tension spring in the sliding contact radio frequency finger of a 212 mm diameter vacuum module, alongside traces of vapor deposition on the various module components with the stainless steel spring material. A comprehensive analysis involving vacuum and beam impedance studies was conducted to investigate the triggering mechanisms behind the warm vacuum module failure. The findings indicate localized beam-induced heating, which could lead to the annealing of the spring with a consequent cascade of effects. Systematic studies of a similar possible failure mechanism for other sizes of vacuum modules were also conducted. Additionally, investigations into potential mitigation measures were performed.