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.

In this paper, the cold-fluid model theory of an intense sheet electron beam is developed to investigate the diocotron instability during its transport in a uniform magnetic field. The model shows that if the magnetic field strength and the beam filling factor are increased separately, the diocotron instability will be suppressed, which extends the sheet-beam transport distance effectively. To verify the above conclusion, a set of complicated instruments, the electron beam measuring and analyzing system (EBMAS), was developed to measure the beam cross section, beam current density, and the 3-D trajectory. The sheet electron beam transport process in a uniform magnetic field with its diocotron instability is investigated on the basis of EBMAS measurements. The measured results agree very well with theoretical calculation and numerical simulation. A sheet-electron-beam tube based on a uniform magnetic field was then manufactured to drive a future W-band sheet-beam klystron (WSBK). Tuning the sheet-beam parameters over a broad range, including a cathode voltage range of 20-82 kV, current range of 0.5-4.27 A, and with a beam cross section of about 10 mm × 0.5 mm, the experimental beam transmission rate is above 98% through a beam tunnel of 100 mm in length.

To study the nonlinear beam-wave interaction for sheet beam klystron (SBK), a 2-D simulation code of SBK2D, based on the 2-D rod macroparticle model, has been designed and realized thoroughly in this paper. In our physical model, the sheet beam is simulated by a series of rods with nonzero thickness and length in y and z directions, respectively (y is the direction of sheet beam's narrow dimension, and z is the direction of beam motion). Then, the space-charge forces between the rod macroparticles are calculated by Green's functions approach, and the port-approximation methods are employed to simulate high-frequency fields for each cavity. Furthermore, the relativistic Lorentz motion equation is solved to obtain the parameters for further macroparticle motion, and the specific criterions are introduced to deal with the sheet beam interception problem by the tunnel and cavities. To verify our simulation code, an eight-cavity W-band SBK has been designed, calculated, and analyzed by SBK2D in detail. The good consistency between SBK2D and 3-dimensional Particle in Cell (3-D PIC) program indicates the reliability of the physical model and simulation code for our program. In addition, the calculation time of SBK2D is only about 1% of that of the 3-D PIC, which makes it more feasible and efficient to calculate and optimize the initial physical parameters for the design of complicated SBK.

A design study for a high-power, high-efficiency, high-growth-rate wideband traveling wave tube (TWT) in W-band using a staggered double-vane slow-wave structure (SWS) combined with three plan alignment pencil beams is described in this paper. The electromagnetic characteristic simulation shows that it has a wide bandwidth, high interaction impedance (about two to three times higher than those of the same structures with the sheet beam scheme), and a more simply designed input/output coupler. 3-D particle-in-cell simulations predict that the TWT can produce over 2000 W of output power from 91 to 95 GHz just using a 52-period two section SWS with a total length of 70.3 mm when the voltage and current of three pencil beams are set to 22 kV and 140 × 3 mA, respectively. The maximum peak output power is about 2256 W with a corresponding gain of 43.5 dB and an electronic efficiency of 12.2% at 94 GHz. The 3-dB bandwidth can be achieved at about 15 GHz with an instantaneous relative bandwidth of about 15.9%. Finally, the comparisons of sheet beam, multiple beam, and single pencil beam staggered double-vane TWT are presented and analyzed.

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.