Secondary Electron Emission from Alumina RF Windows

The development of alumina rf windows used at the output portion of the high-power rf souces is one of the important issues for accelerators. The breakdown of rf windows is caused by: (1) multipactor (electron multiplication on the surface) and/or (2) the discharge of accumulated charges (due to multipactor). In order to produce the durable alumina ceramics, measurements of secondary electron emission (SEE) and surface charging have been carried out. Since excessive surface heating takes place during surface discharge, SEE yields at high temperature were also measured. High-power tests using a resonant ring were examined in order to observe surface charging and electron accumulation. Durable materials were summarized regarding SEE, surface charging and performance under high power tests.