Anti-Breakdown Coatings for High-Gradient Accelerator Structures

Development of accelerator structures that can sustain acceleration gradients up to 150 MeV/m are required in order to build a future multi-TeV collider with an energy reach beyond present or planned electron-positron colliders. Limitations for operation with high acceleration gradient arise from RF breakdown. High-melting-point insulated coatings are to be applied first to test samples and to parts from an experimental SLAC accelerator cavity. Strong adherence of the coating to the underlying copper is to be achieved by use of a graded coating, in which the composition varies smoothly from the copper outwards to the pure insulator. Test elements will also be built for evaluation at 34 GHz, and for coatings on accelerator cavity parts for extensive tests during Phase II. Coatings of ZrO2 on copper were successfully applied, were subjected to adherence tests, and were subjected to thermal cycles to 500