大宽高比的非轴对称带状电子注在微波和毫米波真空电子器件中具有显著的技术优势与应用潜力.采用轴向均匀磁场可以聚焦和传输带状电子注,且具有易于实现电子注与磁场的匹配和调节、聚焦强流电子注以及无传输截止电压限制等优点,但面临严重的Diocotron不稳定性.结合单粒子模型理论和冷流模型理论,对带状电子注传输特性进行的研究及其数值计算表明,通过详细设计带状注电子光学系统物理参数,增强聚焦磁场并在传输通道高度方向上选择较大的电子注填充比,可以有效降低Diocotron不稳定性对带状电子注的影响,并实现其长距离稳定传输.通过对应用于W波段带状注器件的电子枪及电子光学系统三维仿真和参数优化,解决了小尺寸和高精度结构所带来的对准、装配和焊接等工艺与技术问题,完成了带状电子注聚焦与传输实验高真空密封束管的研制.实验获得的电子枪压缩和成形的椭圆带状电子注截面为10mm×0.7mm,且在电子注电压为20—80kV,电流为0.64—4.60A时,在长度为90mm的漂移通道内带状电子注传输的通过率达到95%以上.该结果优于目前国际上采用周期永磁聚焦进行带状电子注传输通过率92%的实验结果.

通过冷流模型理论对均匀场聚焦带状电子注的传输进行了研究,结果表明,通过增强聚焦磁场并提高电子注填充高度因子,可以有效降低Diocotron不稳定性并实现长距离的稳定传输.结合理论研究,对均匀场聚焦带状注电子光学系统进行了三维仿真设计与优化,利用自主开发的二维非线性注波互作用程序SBK2D,对W波段带状注速调管进行了初步分析,结果为输出峰值功率69 kW、效率24%、增益37dB、3dB带宽100 MHz.研制出的具有高机械对准精度的带状注速调管电子束管,带状注截面10 mm×0.5 mm,且在电子注电压20～82 kV,电流0.50～4.27A,长度100 mm的漂移通道内电子注传输直流通过率达到98%以上,高于之前在90 mm漂移通道内获得的95%的实验结果.

A theoretical model is developed for calculating the eigenmodes of the multi-gap resonant cavity. The structure of concern is a kind of ladder-type circuit, offering the advantages of easy fabrication, high characteristic impedance (R/Q), and thermal capacity in the millimeter wave to THz regime. The eigenfunction expansion method is used to establish the field expressions for the gaps and the coupling region. Then, the match conditions at the interface are employed, which leads to a group of complicate boundary equations in the form of an infinite series. To facilitate the mathematical treatments and perform a highly efficient calculation, these boundary equations are transformed into the algebraic forms through the matrix representations. Finally, the concise dispersion equation is obtained. The roots of the dispersion equation include both the axial modes in the gaps, which include the fundamental and the high-order modes, and the cavity modes in the coupling region. Extensive numerical results are presented and the behaviors of the multi-gap resonant cavity are examined.

In this paper, a multigap extended output cavity was designed by 3-D simulations, which served as the output cavity for a W-band sheet-beam extended interaction klystron (SBEIK). In our numerical design, the circuit dimensions were systematically optimized by parametric finite-difference time-domain simulations, and the equivalent circuit for the output cavity was also analyzed. The proper external loading was selected by using a region of loss in 3-D, and the output power was optimized. The results were verified by using the coupler and the waveguide. The 2π mode of the optimized five-gap extended output cavities had an ohmic Q (Q 0 ) of 1343.5, an external Q (Q e ) of 501.6, and a loaded Q (Q L ) of 365.2 at 94.5 GHz. The 3-D particle-in-cell simulations predict that the output cavity of the SBEIK (75 kV and 4 A) can stably produce more than 50 kW of output power using a prebunched beam.

This paper reports the research work of an X-band sheet beam klystron with the aim of principle verification, which is fulfilled at the Institute of Electronics, Chinese Academy of Sciences. This paper includes two phases. The first phase is planned to build the sheet beam electron optics prototype tube using the closed periodically cusped magnetic focusing. The measured data shows that the rectangular beam with the cross section of 50 mm × 4 mm can propagate through ~ 300 mm from the cathode surface to the collector with the transmission of 92.4% at the voltage of 110 kV. This foregoing work successfully solves the beam formation and transportation and becomes the basis for developing the sheet beam klystron. In the second phase, the high-frequency interaction structure is designed and cold tested. The X-band sheet beam klystron is constructed and hot tested in the full voltage. The amplification characteristic can be observed near the voltage of 125 kV. For the drive power of 0.71 kW and the working frequency of 11.69 GHz, the output power of 2.8 MW is achieved with the 3 dB bandwidth of 30 MHz, and, correspondingly, the gain and the efficiency are 35.96 dB and 32.52%, respectively. At the same time, the beam transmission is 73.3%. An over 93% transmission is realized at the voltage of 135 kV, whereas the oscillation occurs in the tube. This research exhibits that the sheet beam klystron is a promising device for the high-power applications, whereas seeking the measures to overcome the oscillation is still an arduous task in the future.