| CPC H01J 1/22 (2013.01) [H01J 35/064 (2019.05)] | 20 Claims |

|
1. A microwave source, comprising:
a cathode heater including a double helix filament, wherein the double helix filament includes a first filament and a second filament; and
a thermionic emitter configured to release electrons when the thermionic emitter is heated by the cathode heater;
wherein when the first filament and the second filament are disposed in a magnetic field and powered by a power source, a first direction of a first current flow in the first filament is opposite to a second direction of a second current flow in the second filament.
|