The coaxial interaction structure for a 0.24-THz, 2-MW gyrotron is designed, and its RF behavior is analyzed for the beam current of 60 A and the beam voltage of 90 kV. The searching of a suitable, very high-order TE mode, which satisfies all the technical conditions required to generate 2-MW RF power, is an important and critical step in the development of a coaxial-cavity (COCA) gyrotron. The detailed analysis of mode selection is described in this article. The geometry of the axially corrugated insert is optimized using an in-house code COCA. Based on the optimized geometry of the coaxial insert and the cylindrical cavity, the coupling coefficient and the start oscillation current are computed to analyze the mode competition for the operating mode TE42,28. The particle-in-cell (PIC) algorithm-based simulation tool is used for the beam–wave interaction computation. Very fine meshing is implemented in the simulations, considering the high frequency and fine geometry of the coaxial insert. The electron beam parameters and the cavity magnetic field are optimized first aiming at the RF power ≥2 MW and frequency 240 GHz. The final results of the cavity design confirm 2.2-MW RF power and 239.975-GHz frequency at 9.74-T magnetic field.

中文翻译：

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用于 0.24-THz、2-MW 回旋管的同轴交互结构的射频行为

设计了0.24-THz、2-MW回旋管的同轴相互作用结构，分析了60 A束流和90 kV束电压下其射频行为。寻找合适的、非常高阶的 TE 模式，满足产生 2 MW 射频功率所需的所有技术条件，是开发同轴腔 (COCA) 回旋管的重要且关键的一步。模式选择的详细分析在本文中进行了描述。轴向波纹刀片的几何形状使用内部代码 COCA 进行了优化。基于优化的同轴插入件和圆柱腔的几何形状，计算耦合系数和启动振荡电流，以分析运行模式 TE42,28 的模式竞争。基于粒子胞内 (PIC) 算法的仿真工具用于束波相互作用计算。考虑到同轴插入件的高频和精细几何形状，在模拟中实现了非常精细的网格划分。电子束参数和腔磁场首先针对射频功率≥2 MW和频率240 GHz进行优化。腔体设计的最终结果证实了 9.74-T 磁场下的 2.2-MW 射频功率和 239.975-GHz 频率。