Investigation and suppression of asymmetric modes competition in Cerenkov device by conductivity anisotropic material loading

Abstract

Efficient and stable operation of Cerenkov devices relies on effective mode control, which means efficient generation of the operation mode and effective suppression of the competition modes. This paper explores the feasibility of suppressing asymmetric modes by loading a conductivity anisotropic material in Cerenkov devices. We theoretically study the dispersion characteristics of a slow-wave structure (SWS) loaded with a conductivity anisotropic material. The theoretical analyses indicate that asymmetric modes such as the HE11 mode have a low net temporal growth rate in a SWS coaxially loaded with the anisotropic material, of which the azimuthal conductivity is in the transition region from good to poor conductor. Accordingly, an anisotropic material with suitable azimuthal conductivity effectively suppresses asymmetric mode competition while maintaining the original characteristics of the symmetric TM modes. Furthermore, we numerically investigate the effectiveness of asymmetric mode suppression by anisotropic material loading using a 3D particle-in-cell CHIPIC code. A coaxially loaded conductivity anisotropic material effectively suppresses the asymmetric HE11 mode in a Ku-band Cerenkov device, and a pure quasi-TEM mode is obtained in the output waveguide. The output power of the generator is 2.9 GW, and the efficiency is 44%. This study provides a feasible method to eliminate asymmetric modes in Cerenkov devices, which may lead to a wide range of applications.

Advancing electromagnetic field modeling in axially anisotropic media with conformal method in 3D cylindrical coordinate systems

“…The RBWO is becoming an international research hotspot in the field of high-power microwave due to its high power, high efficiency and simple structure. Some scholars have used anisotropic media with azimuthal conductivity to suppress the asymmetric mode competition in Cerenkov devices [20,21], making the method proposed in this paper a valuable tool for such devices. Applying this method to PIC simulation, the X-band RBWO shown in figure 9 is selected as the simulation object, figure 9(a) is the case where the anisotropic medium is not filled, and figure 9(b) is the case where the anisotropic medium is filled on the axis.…”

“…However, the overmoded structures can lead to asymmetric mode competition in the device, which can severely reduce the output power and affect the normal operation of the device [14][15][16][17][18][19]. To address this issue, some scholars have proposed a simple and efficient method, which involves filling an anisotropic medium with azimuthal conductivity in the Cerenkov device, effectively suppressing the asymmetric mode competition [20,21]. This method has the advantage of not affecting the working mode of the device and has shown promising results in previous studies [20,21].…”

“…To address this issue, some scholars have proposed a simple and efficient method, which involves filling an anisotropic medium with azimuthal conductivity in the Cerenkov device, effectively suppressing the asymmetric mode competition [20,21]. This method has the advantage of not affecting the working mode of the device and has shown promising results in previous studies [20,21]. At present, the PIC method is frequently employed to simulate high-power microwave devices [22][23][24][25], but there is a lack of literature specifically studying the conformal method in PIC simulation when filling such media in 3D cylindrical coordinate systems, which presents a significant gap in the current research on high-power microwave devices and highlights the need for further studies in this area.…”

“…To demonstrate the applicability of this method to the numerical simulation of high-power microwave devices, it is applied to a 3D cylindrical coordinate system PIC simulation, using an X-band RBWO as the simulation object. Previous studies have shown that the use of an azimuthal conductivity can effectively suppress asymmetric mode competition in the device [20,21]. Therefore, an anisotropic medium with a thickness of 4 mm is filled along the axis of the RBWO.…”

A novel self-injection relativistic backward wave oscillator

“…Moreover, the electron beam interacts with not only the designed operating mode, unexpected beam-wave interaction will decrease the conversion efficiency of the generator [14,[26][27][28][29]. Generally, through designing appropriate beam parameters and dispersion characteristics, the coupling impedance and temporal growth rate of the operating mode are much larger than that of the other modes, which verify the dominant role of the desired mode [30,31].…”