.3 Mm Band Gyrotron High Frequency Window

Output window is one of the key components of the high-power gyrotron. It will have a direct impact on the performance of the gyrotron, or even the whole of the success or failure of development. Therefore, the design of output window of low reflectivity, high-power transmission is an important task in the development of gyrotron .In this paper, on the basis of previous work , designed three type gyrotron output window, done the following major aspects:First, outlined the microwave network knowledge used commonly in the design of the output window gyrotron and the requirements of output window film dielectric material; comparing common characteristics of several dielectric materials. Then through improving the approximate calculation formula of conventional pillbox window obtained approximate calculation formula applicable to the higher frequency of the thick pillbox window. And using high-frequency simulation software HFSS analysised detailly the infection of the pillbox window structure parameters to the output characteristics . Based on the previous calculation formulas and analysis result designed a pillbox output window of gyro-TWT, it is applicable to 3 mm-band transmission power of 50 kW.Secondly, on the basis of the existing circular waveguide output window theory, compiled the optimization calculation programs of output window based on the FORTRAN language ,and using it analysised detailly the structure parameters individually, The numerical calculation results agreed with HFSS results very well. The output window of the center frequency 94 GHz, in the 92.6-95.4 GHz, As the standing wave ratio(VSWR) is less than 1.1, bandwidth of 2.4 GHz. For work in the single-frequency oscillation, the bandwidth can meet its requirements.Again, analysised a three-layer dielectric rectangular high-frequency window, through theoretical calculations abtained the thickness value of the dielectric layers, then simulated comparison by high-frequency simulation software HFSS and CST , the two software simulation results matched well, the curve of the changes of VSWR as the frequency indicating: the window in the 92 GHz center frequency, As VSWR <1.15, the bandwidth of approximately 16 GHz (17.4%). Because of its bandwidth better, and the overall dielectric thickness greater, so it is an ideal choice of the gyro-TWT output window.Finally, analysised the distribution of the electric field of the dielectric surface of these above three windows, given a great deal of pictures of dielectric surface electric field intensity distribution and of horizontal electric field vector ; Calculated temperature difference of dielectric-film surface of pillbox and circular waveguide window on the basis of analysising the tolerance of the transmission of the average power of output window.