中文摘要：

提出了一种新的利用缓变倒向场获得大回旋电子注的设计方法,在分析缓变倒向场中电子的运动规律和引起偏心与速度零散的各种原因的基础上,设计了一支大回旋电子枪.与传统设计思路不同,这种大回旋电子枪既不追求形成薄的管状电子束,又不追求突变的倒向磁场,因而极大降低了制管工艺和结构复杂性;阴极发射带可以位于倒向点前的轴向磁场幅值渐减区域,通过控制各条轨迹起始点的正则角动量差异,并利用多种不利因素的相互抵消作用来减小偏心与速度零散.模拟计算结果与理论分析一致,表明通过微调电磁场使各种不利因素相互抵消可以显著提高大回旋电子束质量,证实了减小偏心与速度零散的调节方法的有效性和实用性.这为高效率大回旋毫米波器件所需的高质量大回旋电子枪提供了一条新的技术途径.

英文摘要：

A novel approach to achieve a large-orbit electron beam is demonstrated using a gradually-changing reversal magnetic field.On the basis of analyzing the general regularities of electron movement and various factors which lead to eccentricity and velocity spread in the gradually-changing reversal magnetic field,we design a large-orbit electron gun.Different from the traditional three-step method,our design does not pursuit the formation of thin tubular electron beam and the utilization of mutation reversal magnetic field,which reduces the difficulties in structure complexity and tube-making process.In addition,the cathode emission band can be placed in the axial magnetic field before the magnetic reversal point where its magnitude decreases gradually,by controlling the angular momentum difference between every trajectory starting points and using the offset effect of various unfavorable factors to reduce eccentricity and velocity spread.The simulation results are consistent with the theoretical analyses,which shows that the beam quality can be improved remarkably by fine-tuning electromagnetic fields,confirms that the efficiency and the applicability of the adjusting method we proposed,and provides a new technical way to obtain a high-quality large-orbit electron beam for high-efficiency large-orbit millimeter-wave devices.