Mitigation of Radio Frequency Breakdown Using Refractory Metal Coatings

Obtaining high-gradient, high frequency accelerator structures are essential for future science, medicine and biology, energy and environment, and national security applications. Emerging experimental results suggest that high magnetic field or alternatively surface pulsed heating leads to radio frequency breakdown. A natural extension is to study materials that have higher tolerance to surface fatigue. Recent work has shown improvements in surface breakdown for ion cyclotron range of frequency antenna for plasma heating can be achieved using refractory metal coatings as compared to pure copper electrodes. The results also suggest additional improvements can be achieved by increasing the density and surface finish of the coatings. Therefore, during this effort Plasma Processes, LLC and Massachusetts Institute of Technology will work together to develop refractory metal coatings with improved density and surface finishes for radio frequency power sources and components for accelerators. During Phase I, parameter development will be performed and samples will be produced for preliminary testing. During Phase II, the techniques necessary for the coating of full-size accelerator components will be developed. Tests of these advanced structures will then be performed yielding critical data on performance. The development of dense, well-bonded refractory metal coatings on copper substrates will enable the fabrication of accelerator components with improved breakdown resistance and improve accelerator performance. In addition, the same techniques used to produce these deposits on copper substrates can be used for other applications including aerospace, defense, propulsion, power generation, electrical contact and switch gear, semiconductor, crucibles, heat shields, x-ray targets, wear and corrosion protection coatings.