Abstract
Asymmetric modes competition in Cerenkov devices were studied with a view to developing a novel method to suppress modes competition, based on loading of the slow-wave structure (SWS) with an anisotropic medium. Due to differences in the field distribution between the asymmetric and symmetric modes, the asymmetric modes are susceptible to significant attenuation in anisotropic media with an appropriate imaginary part for the azimuthal permittivity. In contrast, the symmetric modes, such as the TM01 mode, incur no such losses. Using the EH11 mode as an example, the quality factor obtained from experiments involving the SWS loaded with an anisotropic medium was reduced by approximately 90% compared with that for a copper SWS. The attenuation was sufficiently high that the electromagnetic fields for the asymmetric modes were barely established, indicating that the suppression technique was highly effective. The approach provides a feasible way to eliminate asymmetric modes in high-power microwave (HPM) sources and may lead to a range of new applications in HPM systems.
Highlights
Over the past few decades, the Cerenkov device has become established as one of the most important high-power microwave (HPM) sources given its remarkable operating stability, high output power, and high repetition rate.1–9 mode competition is still a major issue in HPM systems, limiting performance and reducing operational stability.10–18 Generally, mode competition can be categorized into two main types depending on whether the mode competition arises from high-order symmetric modes or asymmetric modes
With regard to asymmetric mode competition, to date, the main methods of suppression include improving the emission uniformity of the cathode,11,20 adjusting both the output and extractor structures,13,14,21 designing a choke mode cavity,11,12 and designing the operation point to be near the upper cut-off of the TM01 mode
Suppression of the asymmetric modes in an Xband slow-wave structure (SWS) has been studied, such that a practical suppression technique was proposed and tested from both a theoretical and an experimental standpoint
Summary
Over the past few decades, the Cerenkov device has become established as one of the most important high-power microwave (HPM) sources given its remarkable operating stability, high output power, and high repetition rate. mode competition is still a major issue in HPM systems, limiting performance and reducing operational stability. Generally, mode competition can be categorized into two main types depending on whether the mode competition arises from high-order symmetric modes or asymmetric modes. With regard to asymmetric mode competition, to date, the main methods of suppression include improving the emission uniformity of the cathode, adjusting both the output and extractor structures, designing a choke mode cavity, and designing the operation point to be near the upper cut-off of the TM01 mode.. Compared with the methods mentioned above, use of an anisotropic medium attenuates significantly the asymmetric modes without incurring losses in the symmetric modes, such as the operating TM01 mode. This approach is attractive and potentially has a wide range of applications in HPM systems
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