The TWT is a wide-bandwidth, velocity-modulated tube used primarily as an amplifier. The electron
beam is bunched by a signal applied to the HELIX. The bunching causes an energy transfer from the
electron beam to the traveling wave on the helix.
The MAGNETRON is a DIODE OSCILLATOR capable of delivering microwave energy at very
high power levels. Three fields exist within a magnetron that influence operation: (1) the DC ELECTRIC
FIELD between the anode and cathode; (2) the AC ELECTRIC FIELD produced by the oscillating
resonant cavities and on the same plane as the dc field; and (3) the MAGNETIC FIELD produced by the
permanent magnet which is perpendicular to the dc electric field.
Magnetrons are of two basic types, the NEGATIVE-RESISTANCE MAGNETRON and the
ELECTRON-RESONANCE MAGNETRON. A diagram of a magnetron is shown at the right.