Thermal Design of Megawatt Power-Level X-Band Coaxial Magnetron

Thermal analysis of X-band high-power (similar to 2 MW) coaxial magnetron is presented. The X-band magnetron is used for a medical linear accelerator (LINAC). The performance of LINAC depends on the RF performance of the magnetron. This magnetron consists of an oxygen-free copper anode with 40 vanes coupled with the coaxial cavity, cooling channels, and an indirectly heated oxide-coated cathode. The operating temperature of the cathode is about 850 degrees C, while the tungsten heater temperature is greater than 1800 degrees C. Therefore, the thermal design of X-band magnetron is a challenging task and it is essential for reliable operation. This article deals with the step-by-step thermal design procedure for each part of this magnetron. The analytical (MATLAB code) calculation of heater temperature for various heater voltages is also carried out for verification of simulation results. By analyzing the temperature uniformity on the emitting surface of the cathode and the effect of the heat film coefficient, it was found that the maximum temperatures on the magnetron anode block, cathode surface, and heater are 220 degrees C, 1045 degrees C, and 1842 degrees C, respectively, for an applied 5-L/min flow rate of water cooling.