A non-uniform three-gap buncher cavity with suppression of transverse-electromagnetic mode leakage in the triaxial klystron amplifier

Abstract

The triaxial klystron amplifier is an efficient high power relativistic klystron amplifier operating at high frequencies due to its coaxial structure with large radius. However, the coaxial structures result in coupling problems among the cavities as the TEM mode is not cut-off in the coaxial tube. Therefore, the suppression of the TEM mode leakage, especially the leakage from the buncher cavity to the input cavity, is crucial in the design of a triaxial klystron amplifier. In this paper, a non-uniform three-gap buncher cavity is proposed to suppress the TEM mode leakage. The cold cavity analysis shows that the non-uniform three-gap buncher cavity can significantly suppress the TEM mode generation compared to a uniform three-gap buncher cavity. Particle-in-cell simulation shows that the power leakage to the input cavity is less than 1.5% of the negative power in the buncher cavity and the buncher cavity can efficiently modulate an intense relativistic electron beam free of self-oscillations. A fundamental current modulation depth of 117% is achieved by employing the proposed non-uniform buncher cavity into an X-band triaxial amplifier, which results in the high efficiency generation of high power microwave. V C 2014 AIP Publishing LLC.

Design and Experimental Demonstration of a Long-pulse, X-band Triaxial Klystron Amplifier with an Asymmetric Input Cavity

“…of 570 kV and a current of 6.4 kA. The beam is guided by an axial magnetic field with amplitude of 1 T. In order to simplify the diode structure of the previous TKAs [5], [6], an asymmetric input cavity is employed. To keep the axial electric field azimuthally symmetric in the gap region, the input microwave is divided equally into two parts by a power divider, and then injected into a reentrant coaxial cavity by two transmission channels, which are composed of some straight, bend and tapered waveguides, as illustrated in Fig.…”

“…The triaxial klystron amplifier (TKA) is an effective solution at high frequencies (such as X-band) to achieve GW level output [1]- [5]. The suppression of the transverse-electromagnetic (TEM) mode leakage among the cavities is crucial in the design of a TKA with high gain, which is effectively resolved by a non-uniform three-gap buncher cavity [6] and specially designed reflectors [5]. The previous investigations mainly focused on the TKA with a radial input cavity [1]- [5], which enabled the electric field azimuthally symmetric in the input cavity.…”