RF sources for accelerator applications are dominated by expensive klystron technologies. Life cycle costs require replacement of the entire microwave tube at the end of life. End-of-life for the RF source is a combination of the power supply design and microwave tube design with failures the result of a combination of these two expensive components where the microwave tube is the fuse. GENERAL STATEMENT OF HOW THIS PROBLEM OR SITUATION IS BEING ADDRESSED. Magnetrons offer a solution to the life cycle costs of klystron technologies for three reasons: 1) Magnetron efficiency is greater by a factor of two or three times that of a klystron, 2) Replacement of the magnetron does not mean replacing the magnet or launcher as is required of a klystron, and 3) The lifetime of the magnetron tube is limited by the filament power supply operation, which can be improved. In this proposal we concentrate on the efficiency enhancement of a 650 MHz magnetron. 900 MHz magnetrons operate at greater than 80% efficiency, while 2.45 MHz magnetrons operate around 70%. It is anticipated that the 650 MHz magnetron efficiency will operate in the 85-90% range. WHAT WILL BE DONE IN PHASE I. In Phase I of the project proposed here, Muons Inc. will design a 650 MHz magnetron prototype to satisfy the requirements of the Solicitation Topic. The efficiency will be optimized by proposed surface treatments of high current regions and the design will incorporate techniques for minimizing the high current regions between the anode and tip of the antenna. The vane and strap anode design will incorporate design improvements to the high current region of the straps by optimizing their geometries. COMMERCIAL APPLICATIONS AND OTHER BENEFITS Muons is a proponent of Mu*STAR Superconducting RF Linac Accelerator Driven Subcritical Molten-Salt Reactors, which can burn Spent Nuclear Fuel (SNF) from past present or future nuclear reactors to make affordable electricity and process heat. Inexpensive and reliable magnetron power sources at 650 MHz are part of our vision to simultaneously turn SNF into a valuable commodity and to produce carbon-free nuclear power to address climate change.