论文标题
来自非均匀阴极的现场辅助热发射的空间充电效应
Space-charge effects in the field-assisted thermionic emission from nonuniform cathodes
论文作者
论文摘要
我们使用计算模拟研究平面真空二极管中的电子发射和传播。我们展示了空间充电如何影响具有两个不同工作函数值的阴极的热发射发射，这些功能构成了阴极表面上有限范围的棋盘格模式。我们确认，对于中间阴极温度，低工作功能区域的局部电流密度可以超过整个阴极的空间充电极限。随着阴极温度的上升，空间充电效应导致发射区域内部的均匀电流密度，并且其外围的电流密度较高。我们展示了光束发射和亮度如何影响，并表明最佳亮度的工作温度使其对应于源限制和空间充电之间的过渡区域有限的发射。最后，我们展示了束电流和光束质量如何取决于阴极的结构的细性。
We use computational simulations to study the electron emission and propagation in planar vacuum diodes. We show how space-charge affects thermionic emission from cathodes with two different values of work function that form a checkerboard pattern of finite extent on the cathode surface. We confirm that, for intermediate cathode temperature, the local current density from low work function regions can exceed the space-charge limit for the entire cathode. As the cathode temperature rises space-charge effects lead to homogeneous current density from the interior of the emitting area and a higher current density from its periphery. We show how beam emittance and brightness are affected, and show that the operating temperature for optimal brightness is such that it corresponds to the transition region between source-limited and space-charge limited emission. Finally we show how beam current and beam quality depend on how fine grained the structure of the cathode is.
