  CW magnetrons, developed for industrial heaters, but driven by an
injection-locking signal were suggested to power Superconducting RF (SRF)
cavities due to higher efficiency and lower cost of generated RF power per Watt
than traditionally used RF sources (klystrons, IOTs, solid-state amplifiers).
When the magnetrons are intended to feed Room Temperature (RT) cavities, the
injected phase or frequency locking signal may provide required phase or
frequency stability of the accelerating field. However, when the magnetron RF
sources are intended to feed high Q-factor SRF cavities, the sources must be
controlled in phase and power in a wide bandwidth to compensate parasitic phase
and amplitude modulations caused by microphonics. In dependence on parameters
of magnetron and the injection-locking signal one can choose regime most
suitable for feeding SRF cavities, enabling magnetron almost coherent
oscillation at the wide bandwidth of control. A novel approach considering
magnetrons as quasi-coherent or coherent RF generators enables choosing the
tube parameters and operation most suitable for various SRF accelerators.
