为北京正负电子对撞机开展的新型电子源实验研究

The quality of the electron beam from a accelerator mostly depends on the performance of its electron source. THe electron source of BEPCⅡ (Beijing Electron Positron Collider upgrate）is based on a thermal cathode HV electron gun, which generates 1ns electron bunch with 120-200KeV energy and several nC charge. In order to match the RF accelarating field of the main accelarator, electron bunch must be compressed from 1ns bunch length into several ps by focus lens and prebuncher and buncher system. We put forwards of a novel elecrtron source technology. A short laser pulse with high power hits a metal wire, and plasma generates. A great amount of hot electrons emits from plasma, and a surface EM wave generates and transports along the wire. Some parts of hot electrons can be guided by EM wave to moves forward along the wire. With the manipulation, we can get a collidmated electron bunch with several nC charge and several ps bunch length for main accelerator. Because the generating process and accelerating process are all from the strong interaction between the laser pulse and wire, the whole system of this kind of lelectron source is much simple than that of BEPCⅡ. It is a promising electron source for BEPC facility.

加速器产生的电子束流品质，很大程度上决定于其电子源的性能。北京正负电子对撞机现有的电子源采用三极枪结构，产生120-200keV、1ns、几个nC的电子束团，经过聚焦、次谐波腔、预群聚、群聚等复杂系统，压缩到皮秒量级后进入直线加速器加速。本项目提出一种新型电子源技术方案，用高功率密度激光脉冲轰击金属丝靶，在轰击位置形成等离子体，有大量热电子飞出，同时在丝靶表面产生表面电磁波。飞出的前向热电子在丝靶表面电磁波的引导下，沿丝靶表面传输，在靶前方位置可以获得指向性好的电子束团，电子能量在0～几百keV连续分布。通过磁场筛选出能量大于100keV、电荷量达nC量级电子束团，进一步压缩到10ps量级。这种新型电子源，电子的产生和加速，都是源自高功率密度激光与金属丝靶的强相互作用，结构简单、造价低，有望发展成为BEPC新电子源技术。

加速器产生的电子束流品质，很大程度上决定于其电子源的性能。北京正负电子对撞机现有的电子源采用三极枪结构，产生120-200keV、1ns、几个nC的电子束团，经过聚焦、次谐波腔、预群聚、群聚等复杂系统，压缩到皮秒量级后进入直线加速器加速。本项目提出一种新型电子源技术方案，用高功率密度激光脉冲轰击金属丝靶，在轰击位置形成等离子体，有大量热电子飞出，同时在丝靶表面产生表面电磁波。飞出的前向热电子在丝靶表面电磁波的引导下，沿丝靶表面传输，在靶前方位置可以获得指向性好的电子束团，电子能量在0～几百keV连续分布。通过磁场筛选出能量大于100keV、电荷量达nC量级电子束团，进一步压缩到10ps量级。这种新型电子源，电子的产生和加速，都是源自高功率密度激光与金属丝靶的强相互作用，结构简单、造价低，有望发展成为BEPC新电子源技术。