摘要
Purpose In order to achieve a high-precision measurement of the incident and the reflected power,a WR1800 rectangular waveguide directional coupler with high directivity and high power level has been in-house developed.Multiple couplers will be installed in the 500-MHz high-power radio-frequency transmission lines delivering 200-kW continuous-wave power for the High Energy Photon Source(HEPS).Methods The directional coupler adopts the design scheme of primary and secondary transmission lines and coaxial coupling-head structure.The shape and dimensional parameters of the coupling head were carefully optimized by using microwave simulation codes.An optimum directivity of 64 dB was achieved in simulations.Results and conclusions A prototype coupler was subsequently manufactured,and its directivity was measured to be 48.2 dB following a rigorous calibration procedure,largely exceeding the design goal and the commercial product.The coupler was then connected to an existing 500-MHz klystron system,and a high-power test with short-circuit termination was conducted.The high directivity of the coupler was confirmed up to 200 kW.During the 6 hours of power aging with continuous-wave 200 kW in a standing-wave setup,no performance degradation was observed on the coupler.The coupler temperature was measured to be 20◦C above the ambient environment.The design requirements were comfortably fulfilled.These constitute thefirst in-house development of a large-size waveguide directional coupler with high directivity and high power level for HEPS.The design,fabrication,and performance tests of the directional coupler are presented.
