Carbon-Fibre-Reinforced Laminates for the Tuning Structure of the LHC RF Cavities

A carbon-fibre-reinforced tube is proposed for the tuning structure of the superconducting RF cavities of the Large Hadron Collider (LHC). It has a high axial stiffness and provides thermal insulation between the cold RF cavity and the tuning actuator at room temperature. The tube is subjected to a high number of mechanical load cycles, high temperature gradients, thermal cycling, and ionizing radiation. Laminate theory is applied to a simplified model of the tube for a failure analysis. Long duration fatigue tests under nominal mechanical and thermal loads were performed on two tubes. The tubes were examined before and after the fatigue tests by geometric measurements, microscopy, and ultrasonic inspection. No damage such as fibre breakage, delamination, or matrix micro cracking could be detected.