Industrial accelerator applications require efficient, scalable, continuous wave (CW) microwave power systems. Magnetrons are inexpensive and efficient devices for converting electrical energy into microwave power; however, their power output is limited to approximately 100 kW. Cost effective power combining magnetron systems would serve the accelerator industry by providing practical and affordable RF power to accelerator applications. In a magic tee configuration, two oscillators can be power combined and locked to a common frequency. Researchers at General Atomics, in collaboration with Thomas Jefferson National Accelerator Facility, have constructed an experiment to demonstrate the power combining of magnetrons in a such a configuration. An analytic model is presented describing the power combining efficiency of a 4-port magic tee, accounting for two magnetron output signals, an injection signal, and a reactive load. The Adler-Chen model is solved numerically using robust computational geometry techniques*. These complete solutions provide insight to the phenomena of magnetron frequency locking and optimal combining efficiency, which are compared to experiment.

The magnetron as an efficient RF source for a compact industrial SRF accelerator has been proposed [1]. The performance of injection phase lock on two independent magnetron transmitters operated at 915 MHz, in CW mode with maximum power of 75 kW each has been demonstrated to satisfy for this application [2]. This industrial type magnetron has transformer and SCR rectifier on the DC anode power supply. Output power spectrum with phase locking can achieve noise reduction of -21 dBc at the 1st 60 Hz, -29 dBc at 1st 120 Hz with only -22.6 dBc injection power. Solenoid current increase of 16% can increase the magnetron relative natural frequency by 4e-4. Further solenoid current modulation with feedback control and the 2x75 kW power combining scheme with the WR975 magic-tee are to be further studied. We intend to use one 75 kW power station with InnoSys' switching DC power supplies to drive normal conducting and superconducting RF cavities for an industrial compact linac. We are also going to report on the 4x1.2 kW power combining experiment on the 2450 MHz magnetron system carried out at GA, including the control algorithm with modified magnetron heads with trim-coils and characterized at JLab.