Electro-thermal analysis of 250 kW coaxial RF window at 350 MHz

Abstract

This paper presents electromagnetic and thermal simulation of a 250 kW 350MHz balanced choke type coaxial RF window including T-bar transition using CST Microwave Studio and ANSYS. The S-parameter analysis of the coaxial widow, using 3D Microwave Studio, has revealed that a match can be found at any frequency between 300 MHz and 1 GHz by suitably tailoring the choke depth independently. Sensitivity analysis has also been carried out to fix manufacturing tolerances. It is found that a deviation of less than 0.1mm in the designed value of choke depth will be tolerable. An integrated design of coaxial window and T-bar transition has been optimized. Using ANSYS3D, electric field, dielectric loss, surface loss, and temperature distributions in the window have been found for 350MHz power transmission up to 1MW. For the power transmission of 250kW, maximum saturated temperature has been found to be 34 °C at the center of the alumina ceramic disc with edge-cooling by water. A cold test model of this window assembly is in the advanced stage of development.