摘要
研究了在预调制成团的电子注经过孔阵列时所激发的Smith-Purcell超辐射现象。基于Smith-Purcell辐射公式,利用三维模拟软件对采用的结构进行模拟仿真,得到在太赫兹频率段的超辐射电磁波。采用对冲光栅来对直流电子注进行调制,理论求解了对冲光栅中的色散方程,并对其进行数值计算,得其色散曲线。选取发射电压U=50kV,发射电流I=30A/cm2,通过色散曲线得到该对冲光栅的注波互作用频率点在0.3THz,最终的仿真结果为0.31THz,两者有较好的吻合度。孔阵列采用的是周期为0.3mm的单排孔阵列,由Smith-Purcell辐射公式计算电子注二次谐波0.62THz的辐射角度为60°,仿真结果与理论分析保持高度一致。通过对辐射区Ez(t)场的观察,发现二次谐波场的幅值是其基波场幅值的5倍多,说明大部分能量集中在二倍频0.62THz上,这与理论分析吻合较好。
An analysis of Smith-Purcell superradiation from subwavelength holes array(SHA) is carried out with the help of three-dimensional Particle-In-Cell code.The two-asymmetric grating is applied to modulate the electron beam and the dispersion curve of the two-asymmetric grating is numerical calculated by MATLAB while the dispersion equation calculated in theory.Using emission voltage U=50 kV,emission current I=30 A/cm2,the wave interaction frequency point is about 0.3 THz which fall into the terahertz regime.The final simulation result is 0.31 THz which matches the theoretical value well.We choose 0.3 mm as the period of the subwavelength hole array.According to the S-P radiation formula,the second harmonic at the frequency of 0.62 THz would radiate at the angle of 60.7° which has good agreement with the simulation result.In the radiation zone,the amplitude of second harmonic wave is five times more than the amplitude of the fundamental wave,which most of the energy is the second harmonic at the frequency 0.62 THz.
出处
《真空电子技术》
2012年第5期22-26,共5页
Vacuum Electronics
