Thermo-Mechanical Analysis of Single-Disc Edge-Cooled Silicon Nitride Millimeter Wave Window for 200 kW CW Gyrotrons

This paper investigates the possibility of using Silicon Nitride Composite (Kyocera SN-287) as single-disc, edge-cooled window for gyrotrons operating below 200 kW CW in the frequency range 28-42 GHz. Rotationally symmetric TE_0n, and TEM₀₀ Gaussian modes of rf transmission through the window have been considered. Analysis performed using a one dimensional (1D) finite difference (FD) code reveals that thermal stresses developed due to non-uniform temperature distribution on the disc surface are well within manageable limits for a 200 kW 42 GHz gyrotron proposed for some ECRH applications. For industrial gyrotrons, for microwave material processing and operating at a maximum power level of 100 kW CW, Si₃N₄ windows may be a cost effective replacement for sapphire windows. It is found that a TE₀₂ profile results in lower peak temperature at the window disc in comparison to a Gaussian beam profile and allows the use of smaller discs.     

Q波段回旋行波管新型盒型输出窗的设计

利用等效电路理论,初步设计了窗片厚度为1.32 mm的回旋行波管盒型输出窗,再加入感性膜片,更改窗片形状,最终设计出了能承受25 kW平均功率、相对带宽达到14%、窗片厚度达到1.7 mm的Q波段新型宽频带回旋行波管盒型输出窗;采用高频软件HFSS与有限元分析软件ANSYS协同仿真的新方法对回旋行波管盒型窗进行热特性研究表明,盒型窗理论上功率容量达到62 kW平均功率,说明输出窗窗片承受25 kW平均功率的可行性,窗片中心与边缘的温差为66 ℃,没有达到陶瓷窗片的临界温差158 ℃,验证了新型盒型窗设计的合理性。     

高功率微波输出窗的介质物理光学分析

讨论了介质物理光学分析方法,并应用该方法数值分析了一个X波段,1.5 GW脉冲功率容量的高斯馈源聚四氟乙烯碟形真空介质输出窗及其辐射场分布。理论计算与实验结果基本一致,从而为优化天线系统打下基础,使用的方法亦可用于厚介质透镜和雷达罩的设计。     

Q波段回旋行波管新型盒型输出窗的设计

利用等效电路理论,初步设计了窗片厚度为1.32mm的回旋行波管盒型输出窗,再加入感性膜片,更改窗片形状,最终设计出了能承受25kW平均功率、相对带宽达到14%、窗片厚度达到1.7mm的Q波段新型宽频带回旋行波管盒型输出窗;采用高频软件HFSS与有限元分析软件ANSYS协同仿真的新方法对回旋行波管盒型窗进行热特性研究表明,盒型窗理论上功率容量达到62kW平均功率,说明输出窗窗片承受25kW平均功率的可行性,窗片中心与边缘的温差为66℃,没有达到陶瓷窗片的临界温差158℃,验证了新型盒型窗设计的合理性。     

Optimized overmoded TE01-to-TM11 mode converters for high-power millimeter wave applications at 70 and 140 GHz

Mode coupling in bent, oversized, smooth-wall circular waveguides was studied by means of numerical integration of coupled-mode differential equations in order to optimize high-power TE01-to-TM11 mode transducers at 70 GHz and 140 GHz. Such mode transformers are used in the mode conversion sequence TEOn to TE01 to TM11 to HE11 for generating the almost perfectly linearly polarized Gaussian-like HE11 mode from circular electric TEOn gyrotron modes. This quasi-optical HE11 hybrid mode is in many respects ideal for electron cyclotron resonance heating (ECRH) of magnetically confined plasmas in thermonuclear fusion research and for other technical applications. Curvature and ellipticity coupling as well as ohmic attenuation of 6 coupled modes (TE01, TM11, TE11, TE12, TE21, TM21) are included in the coupling matrices. Integral expressions were used for deriving the coupling coefficients for arbitrary modes in bent, smooth-wall waveguide. Lowest level of unwanted spurious modes together with highest transmission efficiency (shortest arc length) is achieved with sinusoidal curvature distribution instaed of constant curvature. The calculated conversion efficiencies of 98.0% at 70 GHz and 95.2% at 140 GHz (interior waveguide diameter D=27.8 mm for 200 kW transmission lines) are in excellent agreement with the measured values of (97.6±0.4)% and (95±1)%, respectively.     

用于回旋管测试台的高压电源及控制系统设计

从一套用于回旋管测试台的基于脉冲阶梯调制(PSM)技术的-60 kV DC/50 A高压电源入手,提出了一套基于单片机和现场可编程门阵列(FPGA)的控制系统设计,不仅满足了电源系统各种运行尤其是1 kHz调制的要求以及各种监控的要求,还满足了回旋管测试台的各种逻辑控制与快速联锁保护的要求。最终测试结果表明：该套电源及控制系统逻辑结构清晰,操作简洁,运行可靠,能够满足测试台系统对高压电源各项逻辑控制、精确定时控制、快速保护等控制要求。