  CW magnetrons, initially developed for industrial RF heaters, were suggested
to power RF cavities of superconducting accelerators due to their higher
efficiency and lower cost than traditionally used klystrons, IOTs or
solid-state amplifiers. RF amplifiers driven by a master oscillator serve as
coherent RF sources. CW magnetrons are regenerative RF generators with a huge
regenerative gain. This causes regenerative instability with a large noise when
a magnetron operates with the anode voltage above the threshold of
self-excitation. Traditionally for stabilization of magnetrons is used
injection locking by a quite small signal. Then the magnetron except the
injection locked oscillations may generate noise. This may preclude use of
standard CW magnetrons in some SRF accelerators. Recently we developed briefly
described below a mode for forced RF generation of CW magnetrons when the
magnetron startup is provided by the injected forcing signal and the
regenerative noise is suppressed. The mode is most suitable for powering high
Q-factor SRF cavities.
