  Modern CW or pulsed superconducting accelerators of megawatts beams require
efficient RF sources controllable in phase and power. It is desirable to have
an individual RF power source with power up to hundreds of kW for each
Superconductive RF (SRF) cavity. For pulsed accelerators the pulse duration in
millisecond range is required. The efficiency of the traditional RF sources
(klystrons, IOTs, solid-state amplifiers) in comparison to magnetrons is lower
and the cost of unit of RF power is significantly higher. Typically, the cost
of RF sources and their operation is a significant part of the total project
cost and operation. The magnetron-based RF sources with a cost of power unit of
1-3 dollars per Watt would significantly reduce the capital and operation costs
in comparison with the traditional RF sources. This arouses interest in
magnetron RF sources for use in modern accelerators. A recently developed
kinetic model describing the principle of magnetron operation and subsequent
experiments resulted in an innovative technique producing the "stimulated"
generation of magnetrons powered below the self-excitation threshold voltage.
The magnetron operation in this regime is stable, low noise, controllable in
phase and power, and provides higher efficiency than other types of RF power
sources. It allows operation in CW and pulse modes (at large duty factor). For
pulsed operation this technique does not require pulse modulators to form RF
pulses. It also looks as a promising opportunity to extend magnetron life time.
The developed technique, its experimental verification and a brief explanation
of the kinetic model substantiating the technique are presented and discussed
in this article.
