MULTI-MEGAWATT RF VACUUM WINDOW FOR HIGH DUTY-FACTOR RF ACCELERATING CAVITIES

High power RF vacuum windows used in typical accelerating cavities have historically been difficult to manufacture to meet the demanding electrical and mechanical requirements. In many instances, these items are what limits the power handling of an accelerator. The high electrical fields on the vacuum side of these windows is prone to multipaction breakdown as well as being subjected to high mechanical stresses due to heat and pressure. This proposal will address these technical challenges through known radio frequency engineering approaches as well as developing new methods to minimize insertion loss characteristics while maintaining adequate safety margins against multipaction breakdown. This work will build upon the company’s existing designs and methods for ultra high vacuum windows in use at existing High Energy Physics customer installations. This proposal addressing these technical issues with the development of a vacuum window which operates using alternative waveguide propagation modes that will reduce the E-Field intensity and by application of a non-uniform thickness TiN coating on the vacuum window surface. A window can be developed which will meet power handling requirements outlined in Topic 14a of FOA-0002359. The development will minimize and lower the electric field strength in the structure when compared to traditional designs. This will reduce the critical requirements of the multipacting suppression material deposition. Mechanical design of this window will be vacuum rated and will incorporate arc detection and vacuum pumping ports sufficient to operate in an ambient environment with internal volume evacuated. Future benefits to industry would allow for higher reliability systems in both the high energy physics and medical accelerator markets. These approaches may lead to other advancements in other RF devices subject to multipaction failure such as high power radio frequency loads.