Soane Alexander V, Shapiro Michael A, Stephens Jacob C, Temkin Richard J
Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA. 02139.
IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc. 2017 Sep;45(9):2438-2449. doi: 10.1109/TPS.2017.2726683. Epub 2017 Aug 22.
The linear and nonlinear theory of a gyroamplifier using a confocal waveguide is presented. A quasi-optical approach to describing the modes of a confocal waveguide is derived. Both the equations of motion and the mode excitation equation are derived in detail. The confocal waveguide circuit has the advantage of reducing mode competition but the lack of azimuthal symmetry presents challenges in calculating the gain. In the linear regime, the gain calculated using the exact form factor for the confocal waveguide agrees with an azimuthally averaged form factor. A beamlet code including velocity spread effects has been written to calculate the linear and nonlinear (saturated) gain. It has been successfully benchmarked against the MAGY code for azimuthally symmetric cases. For the confocal waveguide, the beamlet code shows that the saturated gain is reduced when compared with results obtained using an azimuthally averaged form factor. The beamlet code derived here extends the capabilities of nonlinear gyroamplifier theory to configurations that lack azimuthal symmetry.
本文提出了一种使用共焦波导的回旋行波管放大器的线性和非线性理论。推导了一种描述共焦波导模式的准光学方法。详细推导了运动方程和模式激励方程。共焦波导电路具有减少模式竞争的优点，但缺乏方位对称性给增益计算带来了挑战。在线性区域，使用共焦波导的精确形状因子计算的增益与方位平均形状因子一致。编写了一个包含速度扩散效应的子束代码来计算线性和非线性（饱和）增益。它已成功地与方位对称情况下的MAGY代码进行了基准测试。对于共焦波导，子束代码表明，与使用方位平均形状因子获得的结果相比，饱和增益降低了。这里推导的子束代码将非线性回旋行波管放大器理论的能力扩展到缺乏方位对称性的配置。
