Generation of high-brightness electron beams with microfabricated field-emitter arrays

电子束从微细加工的场发射极阵列(FEA)中提取，加速到6keV，传输距离为1m，测量了束流和束流的发射率。主要研究内容如下：1.有限元分析性能研究：研究了自旋阴极和微三极阵列的特性。在1 S状态下，阴极表面的电流密度达到40A/cm2。微三极管阵列演示了平行光束的产生。发射电流的稳定和主动控制：在有限元分析的基础上串联引入场效应管，成功地稳定和控制了发射电流。电子束的远距离传播：从Spindt阴极提取的电子束传播超过1米，并投射到荧光屏上。在那里，形成了有限元分析的放大图像，并分别观察到了尖端的图像。发射度测量：使用静电四极透镜通过拉长屏幕上的图像来测量发射度。分别获得了大电流密度模型Spindt阴极束和小束流的归一化发射率分别为10^~(-7)m-rad和2×10~(-9)m-rad量级。束流亮度：即使在脉冲模式下，当电流密度超过40A/cm^2时，也会损坏FEA。由于这个原因，增加光束亮度的努力已被搁置。FEA的改进：微三极管阵列产生的准直光束由于出口处的杂散电场而严重偏转。我们的合作者正在制造轴对称电极结构的新型场效应管。

Electron beams were extracted from microfabricated field-emitter arrays (FEA), accelarated up to 6 keV,and propagated over a distance of 1 m. Emittances of both the beam and beamlets were measured. The research concerned the following subjects :1. Study of FEA performance : Characteristics of FEAs (the Spindt cathodes and microtriode arrays) were investigated. The current density on the cathode surface reached 40 A/cm^2 in 1 s regime. Microtriode arrays demonstrated the generation of parallel beam.2. Stabilization and active control of emission current : A field effect transistor, introduced in series with the base of FEA,successfully stabilized and controlled the emission current.3. Long range propagation of the beam : Electron beams extracted from the Spindt cathodea were propagated over 1 m and projected on a fluorescent screen. There a magnified image of the FEA was formed and separate images ofthe tips were observed saparately.4. Emittance measurement : An electrostatic quadrupole lens was utilized to measure the emittance by elongating the image on the screen. Normalized emittances of the order of 10^<-7> m-rad and 2 x 10^<-9> m-rad were obtained for beams from high-current-density model Spindt cathodes and a beamlet therefrom, respectively.5. Beam brightness : FEAs were damaged when the current density exceeded 40 A/cm^2 even in the pulsed mode. For this reason, the effort to increase the beam brightness has been suspended.6. Improvement of FEAs : Collimated beams generated by microtriode arrays suffered from severe deflection due to stray electric fields at the exit. New FEAs, axi-symmetric in electrode configuration, are now being fabricated by our collaborators.