To satisfy the space-borne tasks of meteorologic observation, planetary researches, and interferometric imaging, a new trial to develop a high efficiency Ka-band extended interaction klystron (EIK) is put on the agenda. In the high frequency circuit design, it is paid more attention to realizing high efficiency as far as possible; meanwhile, the circuit is kept stable using high lossy bunching cavities. The beam voltage and current are 17 kV and 0.72 A, respectively. The simulated output power is over 3 kW in the bandwidth of >100 MHz, and the maximum efficiency is above 30%. The preliminary test is finished with the beam transmission of 97% and the output power of 2.4 kW.

This paper presents a four-stage DC/DC converter with high precision and a small ripple utilized in an electronic power conditioner (EPC). The galvanically isolated four-stage topology contains four cascade connections: a buck circuit, a push–pull circuit, a power converter, and a voltage regulator. The push–pull switches, as well as the diodes in the output-side rectifier, operate in zero-voltage switching (ZVS) and zero-current switching (ZCS) modes at both switch off and switch on, which helps increase the efficiency. The maximum efficiency of the converter can reach 94.5%. The buck circuit and voltage regulator operate in a two-stage closed-loop condition and, thus, the precision is greater than 0.02%. Due to the voltage regulator, the ripple is less than 1 V when the output voltage reaches 7000 V.

For vacuum electronic devices (VEDs), the use of a hollow electron beam (HEB) increases the beam-wave interaction efficiency and permits a prominent decrease of the cutoff voltage in the focusing-electrode controlled electron gun. To obtain an HEB electron optics system (EOS) with stable propagation, lower ripple, high compression, and good laminarity, the issues related to the HEBs transmission characteristics in a uniform magnetic field are deeply investigated in this article. The studies on the Brillouin flow, which are different from the conclusion of the previous literature, are presented. Through combining the theoretical analysis and the simulation, the distinct motion ways of each layer in the HEB are clearly exhibited in both cases of the immersed flow and the partially shielding flow. This work can provide a meaningful reference for the design of a hollow beam EOS with high transmission and compression.

In this article, the design and experiment of a hollow electron beam (HEB) electron optics system (EOS) for Ka-band extended interaction klystrons (EIKs) are presented. To realize the fast switch of the current emission at a low cutoff voltage, an electron gun with two focus electrodes (FEs) is chosen. The emitting surface of cathode is a ringed spherical surface. The first focus electrode (FE1) is around the cathode, and the second focus electrode (FE2) is set in the central hole of the cathode. The current emitted from the cathode surface is about 2A, when the operating voltage is 25 kV. Three simulation codes, Egun, Superfish, and CST, are used for designing the electron gun and the permanent magnet focusing system (PMFS). Some sensitivity analyses with respect to the PMFS’s critical parameters are presented. The simulation shows the dc beam transmission is 100%. The electron beam, confined by 6000 Gauss uniform field, propagates through the drift tube of 37 mm with good laminarity and small ripple. The emission current can be suppressed when the voltage of the FEs is −3.4 kV. According to the results of simulation, the Ka-band EIK had been constructed and the hot-test experiments had been fulfilled in succession. The experimental results exhibit that the dc beam transmission is about 99% and the beam can sustain 98% transmission at high frequency (HF) operation. In addition, the output power is higher than 8 kW in the bandwidth of over 100 MHz.

This paper presents a two-stage DC/DC converter with high efficiency utilized in an electronic power conditioner (EPC), which is widely applicable in satellite communications, etc. The galvanically isolated converter contains two cascaded converters: a buck converter, which is a pre-regulator operating under a closed-loop condition, and a push–pull converter, which is intended to boost the input voltage, operating under an open-loop condition. In the push–pull converter, the power switches, including the main switches and the rectifier diodes, operate under zero-voltage switching (ZVS) and zero-current switching (ZCS) at both switch off and switch on, which minimizes the switching loss. Furthermore, all of the parasitic parameters, such as the parasitic capacitance, leakage inductance, and magnetizing inductance of the main transformer, are fully utilized. Therefore, the presented topology benefits from fewer semiconductors but higher efficiency. The proposed topology produces less EMI noise because of ZVS and ZCS processes whose fundamental switching frequency interference is relatively low. The presented converter achieves a wide bus voltage regulation range in a satellite because of the pre-regulation of the buck cell. The theoretical analysis is validated by a prototype and its experimental results. The maximum efficiency of the converter can be up to 94.5%, and the high-voltage output is 7000 V.

The Ka-band extended interaction klystrons (EIK) have been developed at the Institute of Electronics, Chinese Academy of Sciences (IECAS), to satisfy the requirement for the high-power millimeter-wave sources in scientific researches. In this work, two kinds of high compression electron gun with the solid or hollow beams, the derivative electron optics systems using the compact permanent magnet uniform focusing and the shared efficient interaction circuit based on the multigap ladder cavity, have been studied in detail and well designed through a mass of calculations. After the mechanical design, finely manufacturing, and a series of technical processes, the Ka-band EIK prototype tubes have been successfully built and tested. For the solid beam scheme, the maximum output power achieves 20 kW in the bandwidth of 60 MHz, and, correspondingly, the gain of 53 dB and the efficiency of 24% are observed. The measured -1 and -3 dB bandwidths are about 220 and 350 MHz, respectively. Meanwhile, the beam transmission is excellent, that is over 97% in dc state and over 90% in RF operation. For the hollow beam case, an over 91% dc transmission test has finished.

In this paper, a W-band rotating TE62 mode is obtained by means of a quasi-optical mode generator in order to test quasi-optical system of the gyrotrons. The quasi-optical generator consists of two mirrors and a coaxial cavity with a perforated outer wall. The simulation results with an electromagnetic analyses software show that the mode purity is up to 96.5%. Processing technologies for components of the mode generator are finished. The assembly device is finished on the basis of the multidimensional localization, which has been tested on the multidimensional automatic test platform.

Thermal and deformation analysis of W-band gyrotron traveling wave tube amplifier (Gyro-TWTA) electron gun are carried out by using the finite element code ANSYS in the paper. Temperature distribution and thermal deformation of the cathode component at given heater power are simulated. These results are verified experimentally in an electron gun. The measured temperature distribution is in agreement with the simulation prediction. Finally, the electron trajectories with and without considering deformation are simulated by EGUN code.

In this paper, a circular TE62 mode generator is simulated and measured in order to test the quasi-optical mode converter system, which would be used in a W-band gyrotron with TE62 mode. The mode generator sequence is rectangular waveguide TE10 - coaxial waveguide TE61 - cylindrical waveguide TE61 - rotating TE61 mode - rotating TE62 mode. Simulation and calculation of the mode generator has been achieved. The optimum converting efficiency of the desired mode is approximately 90%. The output field pattern of the mode generator is presented in a temperature-sensitive liquid crystal display (LCD) sheet by the low-power microwave.

In this paper, the simulation of transverse sweeping system (TFSS) and thermal analysis of undepressed collector for a 94GHz, 30kW CW gyrotron are presented. A smooth power-density distribution profile on the collector is obtained through repeated comparison of the TFSS simulation results, which indicates the range of spent beam spread and the peak power density are about 370mm and 130W/cm(2), respectively. The sensitivities of the TFSS's parameters to the power distribution profile are also studied and analyzed. To avoid the melting of the collector, a cooling channel groove is designed and the thermal analysis with finite element software ANSYS is performed under the non-uniform heat flux. The maximum outer and inner surface temperatures are 94.3 and 102.4 degrees C with water temperature at 20 degrees C, respectively.

In this paper, the design and simulation of a high frequency structure for a W-band quasi-optical gyrotron oscillator, which operates at the TE62 mode, has been presented. According to the self-consistent nonlinear theory, the parameters of the high frequency resonator has been designed and optimized. The effects of electron beam voltage, current, velocity spread, magnetic field and electron beam guiding center on the output power and efficiency have been analyzed. The maximum output power and efficiency of the designed gyrotron oscillator is about 39.7kW and 44.1%, respectively.