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

This paper presents electromagnetic and thermal simulation of a 250 kW 350 MHz 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 0.1 mm 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 350 MHz power transmission up to 1 MW. For the power transmission of 250 kW, 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.