This paper presents the detailed design of a six-beam gun for use in an L-band 10-MW multiple-beam klystron. To facilitate the gun simulation, we developed a joint design methodology with 2-D and 3-D simulation codes. The six-beam gun is designed to produce a total current of 132 A divided equally among the six beams at an accelerating potential of 115 kV. For the design of the gun, special emphasis is placed on the geometric layout of the electrodes to ensure moderate voltage gradient, accurate beam perveance and reasonable cathode loading. The magnetic circuit consists of solenoid magnet structures. Special coils and iron shells are set to ensure a uniform parallel magnetic field in the region between the cathode and the anode. Two set of amendatory coils and shield irons are set in the transition region to optimize the beam radius. Special coils are set in the both ends of the interaction region to trim the radial magnetic fields. The gun design is accomplished with EGUN and CST codes. Simulation results show that the joint design methodology is effective and the magnetic circuit has an excellent flexibility. The final gun has a cathode loading lower than 2.1 A/cm2 and excellent beam transport characteristics. The dependency relationship between the beam off-centering and the asymmetry radial magnetic fields is analyzed.

Six-Beam Gun Design for a High Power Multiple-Beam Klystron

This paper presents experimental results of a novel electron gun with a vacuum-arc-plasma cathode used in microwave tube devices. The plasma cathode is based on a vacuum-arc discharge with a novel hollow anode and a Pierce-type electrostatic focusing system. The experimental result shows that this type of electron gun can be used to generate an electron beam of several amperes with a long pulsewidth. Based on the test results, a longer pulsewidth can theoretically be obtained by adjusting the parameters of the vacuum-arc discharge and ignoring heat dissipation and electrode erosion.

Experimental Study of Electron Gun With Hollow-Anode Vacuum-Arc-Plasma Cathode

Simulation of an electron gun with a high compression ratio for a Ka-band klystron is presented in this abstract The electron gun operates under the voltage of 14kV with a beam current of 1A with a p shaped permanent-magnet focusing structure The beam filling factor is less than 07, and the beam ripple of the average beam radius is about 10% It is helpful for the subsequent engineering practices

Simulation results of an electron optics system for a Ka-band klystron

Input cavity characteristics with a two-beam loading are one of the most important scientific problems for using a two-beam scheme to develop compact, high-power millimeter-wave klystrons. This article focuses on this problem with a 400 kW two-beam loading in an overmoded input cavity which is proposed to develop a Ka-band klystron with peak power toward 150–200 kW. The input cavity exploits TM13 mode to support two equivalent sections of field gaps for modulating two beams. The beam loading parameters, such as <inline-formula> <tex-math notation="LaTeX">${P}_{t}$ </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">${Q}_{b}$ </tex-math></inline-formula>, and cavity parameters, such as electric field distribution, frequency (<inline-formula> <tex-math notation="LaTeX">${f}$ </tex-math></inline-formula>), and cavity <inline-formula> <tex-math notation="LaTeX">${Q}_{l}$ </tex-math></inline-formula> without beams can be optimized and selected to achieve matching absorption by two beams with a certain RF power injection in the Ka-band. The CST Studio Suite (CST) simulation results show that over 99% power of the input signal around 35 GHz can be absorbed by the input cavity loaded by two beams with <inline-formula> <tex-math notation="LaTeX">${P}_{t}$ </tex-math></inline-formula> of 0.473–<inline-formula> <tex-math notation="LaTeX">$0.716~\mu \text{P}$ </tex-math></inline-formula>. Constant <inline-formula> <tex-math notation="LaTeX">${P}_{t}$ </tex-math></inline-formula> exercises about the same degree of two-beam loading on the input cavity.

Study of the Input Cavity Characteristics With Two-Beam Loading for Developing a Compact and High-Power Ka-Band Klystron

This paper presents the simulation study of the dispersion and interaction impedance of the disc-loaded waveguide structure using periodic boundary method, resonant method and perturbation method. Relationship between the structure dimension and the high-frequency characteristics are analyzed.

Analysis for RF character of the disc-loaded waveguide structure

This paper presents the design and experimental results of the electron optics system for use in an S-band 100-MW high-peak-power klystron. The gun operating voltage is 415 kV with a beam current of 535 A. For the design of the gun, special emphasis is placed on the geometric layout of the electrodes to ensure a moderate voltage gradient, reasonable cathode loading, and accurate beam perveance. The beam-focusing system is a space-charge balanced flow type with a solenoidal magnet structure. The magnetic field at the center of the cathode is 60 G, and the longitudinal magnetic field in the interaction region is in the range of 1.0-1.38 kG. The electron optics system design was accomplished with SUPERFISH, EGUN, and a Particle-in-Cell (PIC) code. Simulation results indicate that the gun has a voltage gradient lower than 220 kV/cm and excellent beam transport characteristics with a beam-to-tunnel radial fill factor of less than 0.75. The focusing beam trajectories simulated by EGUN and the PIC code both have good laminarity. Two prototypes based on a simplified RF design (not intended to achieve full RF power) were fabricated in order to demonstrate the beam optics, and the measured beam transport is in agreement with predictions made by simulation codes. RF circuit simulation designs with the 1-D large-signal code KLY_12 and the PIC code are also presented.

Electron Optics System of a 100-MW S-Band Klystron

As trapped higher-order modes can possibly cause self-oscillations of three-gap coupled cavity, which may be a crucial influence on EIK's operation and performance, of great importance is analysis of modes stability through calculating the beam-loading conductance of higher-order modes. In this paper, a three-gap cavity in Ka-Band is designed in HFSS environment, which is followed by calculation and analysis of beam-loading conductance.

Analysis of the beam-loading conductance in three-gap coupled cavity

In this paper, by means of a 3D particle-in-cell (PIC) code, the non-linear calculation of beam-wave interaction in periodic cusped magnetic (PCM) field is presented for the X-band sheet beam klystron with five three-cell, extended interaction cavities. The simulation results show that the output peak power is more than 32.4MW, with the interaction efficiency of more than 31.2%, and the gain of more than 35.6dB.

Interaction simulation of an X-band sheet beam klystron

Study of the Performance Improvement on Coaxial Output Cavity for Higher-order Mode Multiple-beam Klystron: Study of the Performance Improvement on Coaxial Output Cavity for Higher-order Mode Multiple-beam Klystron

A coaxial output cavity with reentrant ring and short circuit pole for multiple-beam klystron (MBK) is presented, which can increase the frequency interval between operating mode TM 310 and neighboring modes to more than 1.0 GHz in X-band, diminish the external Q-factor from 535.4 to 202.2, and make the field distribution of TM 310 mode symmetrical enough. The simulation results are obtained by CST-MWS.

Huipeng Han

Papers

Electron Optics System of a 100-MW S-Band Klystron

Analysis of the beam-loading conductance in three-gap coupled cavity

Interaction simulation of an X-band sheet beam klystron

Study of the Performance Improvement on Coaxial Output Cavity for Higher-order Mode Multiple-beam Klystron: Study of the Performance Improvement on Coaxial Output Cavity for Higher-order Mode Multiple-beam Klystron

P1–10: Study of coaxial output cavity for multiple-beam klystron