Phase and Frequency Locked Magnetrons for SRF Sources

Typically, high power sources for accelerator applications are composed of many megawatt microwave tubes that are combined together to form ultra high-power localized power stations. The RF power is then distributed to multiple strings of cavities through high power waveguide systems, which are expensive to produce and operate. Alternatively, the more efficient magnetrons could be used as the microwave source, but there have been problems with respect to their frequency and phase stability. This project will utilize a recently developed variable-frequency cavity technique to phase and frequency-lock magnetrons, allowing their use for either individual cavities, or cavity strings. In Phase I, thin ferrite or YIG (yttrium iron garnet) blocks will be brazed into the regions of high magnetic field of selected ordinary magnetrons. A variable external magnetic field, orthogonal to the magnetic RF field of the magnetron, will surround the magnetron to vary the permeability of the ferrite or YIG material. A feed-back loop will be designed and built to control the magnetic field, which in turn will control the phase and frequency. A full system will be demonstrated in Phase II. Commercial Applications and other Benefits as described by the awardee: Magnetron sources with built in phase and frequency stabilizing structures would have broad applications, from sputtering systems to phased array radars, as well as small to large accelerator systems.