A 0.3 THz Multi-Beam Extended Interaction Klystron Based on TM10,1,0 Mode Coaxial Coupled Cavity

Fu-Min Lin,Yujie Xiao,Liangxian Zhang,Shuning Wu

doi:10.1109/access.2020.3040394

Abstract

A new conceive of high-order mode multi-beam Extended interaction Klystron (EIK) at the terahertz (THz) band is proposed. The interaction circuit based on the coaxial coupled cavity at ${\mathrm {TM}}_{\mathrm {10,1,0}} - 2\pi $ mode is designed and analyzed. Benefiting from the larger transverse space of the coaxial coupled cavity operating at high-order mode, multiple electron beams are formatted to reduce the current density of each electron beam. The crucial parameters associated with the interaction are determined by theoretical calculation and optimized by three-dimensional (3D) Particle-in-Cell (PIC) simulation. The results of theoretical analysis and PIC simulation demonstrate that the EIK operates at ${\mathrm {TM}}_{\mathrm {10,1,0}} - 2\pi $ mode without mode competition and self-oscillation. Driven by ten individual electron beams with the voltage of 20 kV, the current of 0.1 A and the current density of 318 A/cm2, the maximum gain of 48 dB is achieved at the center frequency of 300 GHz with a 3-dB gain bandwidth of 200 MHz. And the corresponding output power and efficiency are 312.5 W and 1.56 %. The results indicate that the proposed EIK is a practical approach to generate high power terahertz waves using the thermal beam with a low compression ratio.

Highlights

The extended interaction device is a kind of vacuum electron device with high power, efficiency and reliability at millimeter and sub-millimeter wave frequencies, including Extended interaction Klystron (EIK) and Extended interaction Oscillator (EIO)
Conventional EIK is facing a series of difficulties when it extends to the THz band, the most prominent of which is the rapidly reduced dimension and the higher requirement of the current density of the electron beam
To deal with these problems, a novel TM10,1,0 mode multi-beam extended interaction klystron is proposed in this paper, and the interaction circuit including the coaxial coupled cavity and the multi-extraction output cavity are designed and analyzed, and the crucial structure parameters are determined

Summary

INTRODUCTION

The extended interaction device is a kind of vacuum electron device with high power, efficiency and reliability at millimeter and sub-millimeter wave frequencies, including Extended interaction Klystron (EIK) and Extended interaction Oscillator (EIO). Lin et al.: 0.3 THz Multi-Beam EIK Based on TM10,1,0 Mode Coaxial Coupled Cavity TABLE 1. The propagation of the electromagnetic waves in the beam tunnel is difficult to be cut off completely, which causes the signal feedback between cavities and results in the undesired oscillation Another potential approach is to use the multi-beam interaction system to reduce the current density of beams [13], [14]. Our EIK operates with the beam voltage of 20 kV, the optimum gap length of the bunching cavity is 0.11 mm and that of the output cavity is 0.13 mm, as shown in Fig. 3(a) and Fig. 3(b), respectively. If the operating beam voltage is determined, the period length L of the coupled cavity can be calculated by. We make vp equal to v0, and the beam voltage at this condition is called synchronous voltage

BEAM PARAMETERS

STABILITY ANALYSIS

CONCLUSION