NSLS-II Seminar

State-of-art techniques will be covered in high-power microwave beam shaping and transmission for frequency-tunable (4-frequency/mode), 1 Mega-Watts gyrotron design. Gyrtron is a high-power microwave generator that converts near-relativistic gryrating electron beam energy into microwave, which can produces pulsed or continuous wave power up to Mega-Watts at frequency greater than 100 GHz, with possible applications in plasma heating, material sintering, deep space communication and so on. The demand for frequency-tunable microwave beam-shaping and transmission for gyrotron is of great interest and poses a challenge for high-power microwave scientists and engineers. We have successfully designed such a 4-frequency/mode (TE21,6 at 107.5 GHz, TE22,6 at 110 GHz, TE24,7 at 124.5 GHz, TE25,7 at 127.5 GHz) tunable system for CPI-type 1MW gyrotron, with overall power efficiency greater than 99.4% at the gyrotron output Brewster window. Many of these design techniques will be covered in this talk, which include TE mode converter, Gaussian beam shaping by aluminum/copper mirrors, Brewster diamond window for Gaussian beam transmission, high-order mode effect in resonant microwave cavity, shaping Gaussian beam into flat-top beam and so on. Design result and computer simulation (HFSS, Surf3d, Cascade) will be shown. Cold test facility based on superheterodyne technique will be discussed. Cold test result will be given, along with hot test result carried out by CPI.