Design and Simulation of an S-Band Relativistic Inverted Magnetron

A high-power relativistic inverted magnetron oscillator (IMO) operating in the S-band is designed and numerically simulated using the massively parallel electromagnetic particle-in-cell code [improved concurrent electromagnetic particle-incell code (ICEPIC)]. This inverted magnetron is designed for optimum operation at ~2.5 GHz for magnetic fields ranging from 0.09 to 0.15 T and voltages extending from ~190 to 360 kV. Simulations in the above mentioned voltage/magnetic field range predict a device capable of operating in a single dominant π mode with little to no mode competition, fast startup times, and high output power exceeding 500 MW in many cases sampled. This design eliminates a common source of energy loss in standard relativistic magnetrons and downstream end-loss current. The IMO also eliminates the need for extended waveguide structures and combiners common for magnetrons that require radial RF extraction. This is done by radiating RF energy axially through the use of a dual-ring radiator. The dual-ring radiator excites the TM01 mode in a single downstream waveguide that maybe then directed toward an antenna. The S-band IMO-simulated RF output power efficiencies are typically near 15% with RF output power ranging from 250 MW to ~1 GW at the highest voltages sampled. ICEPIC models show key segments of the design that may undergo excessive electromagnetic field stress during saturation. Such stress may ultimately lead to plasma formation and performance degradation; however, this may be mitigated via alternate materials, voltage derating, and further design refinement. In the simulation, the S-band IMO exhibits stable, robust, and reliable performance in the desired mode over a range of voltages and magnetic fields.