X-band RF structure thermal analysis and tests

The design of X-band multi-cell RF structures for particle accelerators requires an accurate estimation of the sensitivity to the mechanical deformations induced by the surface power loss on the metallic walls. The prediction of these effects is important for conceiving a tuning strategy that assures the correct structure operation when integrated into the accelerator complex. An experimental technique is proposed for preliminary testing of the mechanical deformations caused by a thermal load that can generate in the RF cavity a temperature gradient profile as close as possible to the real one induced by the electromagnetic power loss. Because we want to find a method that can be easily and cheaply implemented in the laboratory, a thermal radiator with uniform heating power density, placed on the axis of the RF cavity, has been chosen as heating source. A multi-physics finite-element code (ANSYS) has allowed comparing the measured temperature gradients with the computed ones. The good agreement validates the application of the code, which has been extended to the joint solution of the electromagnetic and thermal problem. Thus the sensitivity to deformations can be directly evaluated.