A radio frequency magnetron device for generating radio frequency power includes a cathode at least partially formed from a diamond material. An anode is disposed concentrically around the cathode. An electron field is provided radially between the anode and the cathode. First and second oppositely charged pole pieces are operatively connected to the cathode for producing a magnetic field in a direction perpendicular to the electric field. A filament is provided within the electron tube which when heated produces primary electrons. Alternatively, a voltage is applied to the anode which causes primary electrons to emit from the diamond coated cathode. A portion of the primary electrons travel in a circular path and induce radio frequency power. Another portion of the primary electrons spiral back and collide with the cathode causing the emission of secondary electrons. The secondary electron emission sustains operation of the magnetron device once the device has been started.