基于光栅结构的自由电子激光波荡器(特邀)

Free Electron Laser Undulator Based on Grating Structure(Invited)

波荡器是自由电子激光器的关键技术部件,目前常规的波荡器主要由磁体构成,利用磁场实现电子束偏转振荡,将电子束能量耦合至激光场。本文提出一种基于光栅表面电场的电波荡器机制,以发展自由电子激光器的小型化技术。阐述了该波荡器的基本原理及电子束在波荡器中的运动规律,推导了该方案下的自由电子激光波长及增益,对所采用的光栅表面电场进行二维仿真,并对电子束进行了跟踪仿真,计算了能量10 MeV电子束产生的激光增益为0.43,验证了基于光栅结构的微纳波荡器方案的可行性。

Free electron laser light source is a new type of coherent light source.It has many advantages such as wide wavelength range,pure spectrum,high power and so on.It has significant application requirements in biology,materials,medicine and other fields.Therefore,since the invention of free electron laser theory in the 1970s,free electron laser technology has been developed rapidly.The principle of free electron laser is to make use of electron beam oscillation in periodic electromagnetic field to produce electromagnetic radiation.By controlling the oscillation period,the magnetic radiation light forms coherent radiation.The undulator is a key technical component of free electron laser,which is used to generate the periodic electromagnetic field that oscillates the electron beam.At present,the undulator is usually composed of magnets,and uses magnetic field to realize deflection oscillation of electron beam,coupling the energy of electron beam to the laser field.In 1988,researchers at the Institute of High Energy Physics of the Chinese Academy of Sciences proposed a free electron laser scheme based on ferroelectrics generating transverse deflecting electric fields.Nearly 30 years,laser technology and processing technology have obtained fast development,leading to a series of micro accelerator innovation,with many new accelerators constantly emerging,such as metal surface laser accelerators and medium-sized laser accelerators,and a large number of researchers around the world constantly promoting micro accelerator technology forward.Inspired by lateral deflection field free electron laser solutions,and benefit from the development of laser,micro-nano technology in recent years,this paper puts forward a kind of miniature undulator,based on the structure of grating with femtosecond laser pulses irradiation grating.The periodic transverse deflection electric field is formed on the surface of the grating,and the high energy electron beam is modulated by the periodic electric field,which generates periodic oscillation and radiates coherent electromagnetic wave to form a gain of free electron laser.In this paper,the free electron laser vibrator with grating structure is theoretically analyzed,the trajectory equation of electron beam is given,and the electric field simulation of the structure is carried out to obtain the transverse electric field distribution on the surface of the grating.Finally,a 10 MeV electron beam with 10 mA intensity is tracked,and the laser gain is calculated.