A Phase-Controlled Magnetron Using a Modulated Electron Source

Magnetrons are efficient and robust, but phase-controlled magnetrons are difficult to implement. Our prior work [1] has used 2D simulations of a rising sun magnetron to demonstrate that the magnetron phase can be controlled by modulating the electron injection at discrete locations to control formation of the electron spokes. These results have further shown that such phase control can be achieved if only 10% of the injected current is modulated. We are currently designing a magnetron experiment that will use the 10-cavity circuit of a commercially available cooker magnetron from L3 Communications. Although the CWM-75KW magnetron can operate at high power (75 kW), our experiment will utilize the devices ability to operate at lower power and voltage (<1.5 kW and < -12kV) at 900 MHz. In addition, the device can operate at very low injected current (<200 mA). The modulated current will be provided by Gated Field Emission Arrays [2] that have demonstrated current densities of 100 A/cm²  at a gate to emitter bias of < 75 V. For this experiment, the GFEAs will only need to operate at a peak current density of < 200 mA/cm² . The experiment will utilize a 10-sided faceted cathode constructed of a lower temperature co-fired ceramic (LTCC) that uses electron hop funnels to protect the GFEAs. Impedance matched address lines fabricated within the LTCC will drive the GFEAs which must be modulated at 900 MHz or an odd sub-harmonic (300 MHz). The cathode structure fabrication, GFEA implementation, drive electronics, and drive scheme will all be presented.