Dongping Gao

Theoretical Investigation and Simulation of Resonant System of Sector and Hole-and-Slot Resonator Type Rising-Sun Magnetron

In this paper, a sector-step approximation (SSA) model is introduced. With step admittance recurrence and field matching relation, the dispersion equation of rising-sun magnetron (RSM) with arbitrary resonators is derived. By this model, resonant frequencies of a 10-resonator sector and hole-and-slot resonator type RSM (SHSRSM) are theoretically calculated. In addition, computer simulation is performed to verify the accuracy of the theory. Besides, the effects of the hole radius on magnetrons main characteristic parameters are analyzed, such as π-mode resonant frequency, mode separation, and quality factor. The optimized SHSRSM is compared with two common kinds of RSMs, such as sector resonator type RSM (SRSM) and sector-and-slot resonator type RSM (SSRSM). The results show that the theoretical results are well consistent with the simulation results, and the maximum relative error is less than 3%, which verifies the accuracy and feasibility of the SSA model. Compared with SRSM and SSRSM, SHSRSM has greater mode separation and quality factor, which improves the stability and the energy storage of RSM.

Equivalent Circuit Method of Resonant System of Magnetron With Sector-and-Slot Resonant Cavities

In this paper, the equivalent capacitance and inductance of sector-and-slot resonant cavities are investigated theoretically by the equivalent circuit method. Thereby, the expression of the resonance frequency is obtained as a function of structure dimensions. In addition, the effects of structure dimensions on equivalent capacitance, inductance, and π-mode frequency are analyzed numerically, especially the slot width, slot length, and height. The results show that, compared with field theory, the equivalent circuit method is in more consistent with the simulation results, which verifies the validity of the equivalent circuit method. With the given structure dimensions, the equivalent capacitance increases with the increasing of slot length and height or the decreasing of slot width, while the equivalent inductance is opposite. Therefore, the change tendency of resonance frequency is determined by the relative changes of the capacitance, inductance, and coupling capacitance. This method can help to predesign and analyze resonant system of magnetrons with sector-and-slot resonant cavities efficiently.

Design and calculation of an S-band high-average power broadband multi-beam klystrons

An S-band high average power broadband MBK with peak power of 500kW, average power of 30kW and relative bandwidth of 10% is being developed in the Institute of Electronics, Chinese Academy of Sciences (IECAS). Two types of RF interaction system, cylindrical cavity and coaxial cavity are going to be used for getting required performance. The calculation results and relative technical problems for developing this MBK will also be given.

Numerical Simulation and Experiment of Hardening Behaviors in Unsaturated Polyester Resin Artificial Marble Blocks Under Microwave Radiation

A high-power continuous microwave hardening system at the frequency of 915 MHz and the maximum output power of 60 kW is established to harden unsaturated polyester resin (UPR) artificial marble blocks of typical size 1600 x 900 x 600 mm3 in the industrial production. The microwave hardening system contains three major sections, including a 2000x1300x900 mm3 multimode cavity, microwave generators, and three groups of feeding-waveguide systems from microwave generators to the multimode cavity. An optimum hardening method by adjusting the value of incident power and processing time is found on the basis of study of UPR properties and can promote products qualities. A numerical coupled electromagnetic and heat transfer model has been built to simulate microwave hardening process and to predict temperature profiles of artificial marble blocks successfully. The result that there is no significant change in temperature profiles between fixed and temperaturedependent thermal parameters indicates thermal conductivity K and specific heat capacity CP, which are not sensitive to temperature. The effect of height between artificial marble block and cavity bottom on electromagnetic field, absorption power, and temperature distribution is also discussed in this paper. The contrast results between the two hardening methods prove that the microwave hardening can achieve better comprehensive characteristics than natural hardening. The establishment of the high-power microwave hardening system has improved the industrial production efficiency of UPR artificial marble 300 times.

The research on parasitic RF output of Multi-Beam Klystrons

The high order mode oscillation and parasitic RF output have serious influence on the normal operation and the purity of the output spectrum of MBKs. By putting a microwave absorbing block in the coupling slot of the double-gap coupling cavity, all the high order modes with π mode field structure can be suppressed effectively. The experiment indicated that the size and shape of the absorbing block have big influence on the stability of the MBK. The influence of the absorbing block on the properties of the modes in double gap coupling cavity (DGCC) is calculated and analyzed in this paper. By using PIC code, the beam-wave interaction in DGCC is also calculated. Based on above calculations, it is possible to determine the suitable size and shape of absorbing block while keeping the MBKs operate stable on the high power level.

Progress of an S-band high average power broadband multi-beam klystron

An S-band high average power MBK producing peak power of 500kW and average power of 30 kW over 10% of relative bandwidth has been designed in Institute of Electronics, Chinese Academy of Sciences (IECAS). Two klystrons are manufactured and have been well tested. Fundamental mode was chosen for RF interaction system, and both calculation and experimental results will also be addressed in this paper.

Research and Development of S-Band High Power Multibeam Klystron

The design, manufacture, and test of an S-band high power multibeam klystron (MBK) are presented in this paper. The test results indicate that the performance of the MBK satisfies the design requirement. Several technical problems, such as the oscillation of high-order modes, a decrease of the beam current under no-driver (oscillating) conditions, and the high-voltage breakdown are also discussed. Some improvements have been taken to overcome these problems. The improved tube has a beam transmission rate over 98%, and operates very stably under DC and RF conditions.

Development of an S-Band High Average Power Multibeam Klystron With Bandwidth of 10%

An S-band high average power multibeam klystron (MBK) producing peak power of 500 kW and average power of 30 kW over 10% of relative simultaneous bandwidth has been designed and developed in Institute of Electronics, Chinese Academy of Sciences (IECAS). The biggest challenges were achieving over 10% relative simultaneous bandwidth performance with higher efficiency at the same time and focusing and transport of the intense electron beam because of the highest level average power in all types of MBKs in IECAS. Two prototypes were manufactured and both have been thoroughly tested. The fundamental mode was chosen for the RF interaction system, 24 beams are used to obtain a beam current of 50 A and the beam voltage is 29 kV. The efficiency is greater than 40% and the gain is greater than 37.5 dB over a relative simultaneous bandwidth of 10%. Both design considerations and experimental results have been addressed in this paper. The experimental results are close to design specifications.

Development of a 2.5-Dimensional Particle-In-Cell Code for Efficient High-Power Klystron Design

In order to efficiently study the complex nonlinear beam-wave interaction in high-power klystrons, we have developed a 2.5-D code, named, KLY2D, based on a theoretical model combining particle-in-cell (PIC) method and finite-difference time-domain (FDTD) algorithm together. In the model, the particle charge and the beam current are properly assigned onto the grids based on the PIC method; the FDTD algorithm is introduced to solve Maxwells equations so that the space charge of the electron beam can be accurately calculated, and the port-approximation method is employed to simulate high-frequency cavity fields; finally, the Lorentz motion equation is solved to further advance particle motion. This 2.5-D model is more accurate than the simple 1-D nonlinear code. For the cylindrical structure of a normal klystron, the port-approximation cavity model is accurate enough to model field-to-beam effect and saves much more computer resource than the full 3-D PIC model. This code is benchmarked on an S-band 50-MW high-peak-power klystron. The good consistency between the theoretical results and the experimental data indicates the reliability of the theoretical model and the simulation code, which is of importance for further promoting the design and the development of high-power klystrons.

Initial analysis of a coupled-cavity EIO

This paper presents the design and analysis of a 220GHz EIO with coupled-cavity structure. The dispersion curve is decided by using periodic boundary method and resonant method. The field distribution of the 2π modes is presented. Relationship between the structure dimension and the dispersion characteristics are analyzed. Detailed structure parameters of a 2π mode 220GHz coupled-cavity for an EIO are presented. A 7 periods coupled cavity structure predicts an output power of 38W by using an electron beam with 13kV voltage and 0.105A current.