Development of an Electron Linac for Radiation Therapy. I. Suppression of Cathode Back-Bombardment Effect

The article is devoted to the development of an electron linac for the radiation therapy complex ‘‘Onyx.’’ A brief overview of the accelerator is provided, and the main problems encountered during its development are highlighted. The core of the article addresses the solution to the most critical of them, related to the back bombardment of the electron gun cathode, which led to instability in the gun current and the bremsstrahlung dose rate over time. The modifications made to the design of the accelerating structure and electron gun, which helped eliminate the back-bombardment problem and achieve the required stability of the bremsstrahlung parameters, are described.