Measurements of high-temperature RF and microwave properties of selected aluminas and ferrites used in accelerators

Modern accelerator design practice includes the use of alumina RF and microwave windows and high-quality ferrites in applications with ever-increasing requirements on power handling ability. Modeling studies of such designs are of increasing economic importance, but frequently are hindered by a lack of measured values of the ceramic loss factors. AECL has developed a system to measure the complex permittivity of small samples over a frequency range from 50 to 2450 MHz and up to 1000 degrees C in temperature. Samples of RF window materials from several suppliers have been studied, with a view to relating the dielectric loss factor to the microscopic material properties. The temperature dependence of the dielectric and magnetic loss factors of a few relevant ferrites were measured at selected frequencies. The measuring methods are described, and the results are presneted.<>