Research on Small Sized Free Electron Laser Using Hybrid Helical Microwiggler

自由电子激光(FEL)实验仅在装有高能电子束加速器的大型设施中进行。这一事实阻碍了许多研究人员轻松使用自由电子激光。因此，研制一种甚至可以在普通大学实验室中使用的小型自由电子激光器是非常重要的。自由电子激光作为远红外到毫米波的低功率光谱光源可以解决这一问题。在这项研究中，我们试图将自由电子激光的每个组成部分尽可能地小型化，一个微摆荡器和一个基于场发射的电子束源。摇摆器场的计算机模拟分析决定制作一种每个周期四层结构的混合螺旋微摆荡器。每一层由五角形永磁体和铁磁体组成，沿摇摆器轴旋转90°角堆积。摇摆器的周期直径为10 mm，间隙直径为5 mm。摇摆场被测量为足以用于FEL 3.8Kg，且可以是adjus…在200G以内，更均匀的磁场将通过对永磁体的分选实现。摇摆器的高度只有75毫米，这意味着它是世界上最小的微摇器之一。除了FIR FEL外，该摇摆器还引起了一些研究人员对短波SASEFEL和伽马-伽马对撞机的兴趣。在场发射实验中，将传统的钨丝电解刻蚀到针头上进行研究。模拟和实验发现，在一定的第二栅电压范围内，电子束电流随阴极电位和第一、二栅间距的增加而增大。四根钨针可以很好地排列。聚束碳纳米管也被提供给场发射源研究。获得了高达2.2 mA的场发射电流，约为W针尖的100倍。目前的波动也非常小&lt；4%。可以说，我们的纳米管目前已经具备了切伦科夫自由电子激光或史密斯-珀塞尔自由电子激光所必需的性质。进一步的研究正在进行中，即将电子束传输到摇摆器中并发射辐射。较少

Free electron laser(FEL) experiments have been done only in huge facilities containing high energy electron beam accelerator. This fact prevents many researchers from easy use of FEL. It is, therefore, very important to develop a very small scale FEL which can be used even in normal laboratory of university. This problem could be resolved for FEL as spectroscopic source with low power in the far-infrared to millimeter wave. In this study, we tried to develop each constituent of FEL as small as possible ; a microwiggler and an electron beam source based on field emission.A computer simulation analysis of wiggler field decided to manufacture a hybrid helical microwiggler constructed with four layers each period. Each layer consists of pentagonal permanent magnets and ferromagnets and is stacked along the wiggler axis rotating angle of 90°. The period and gap diameter of the wiggler are 10 and 5 mm, respectively. The wiggler field was measure to be 3.8 kG enough for FEL and could be adjus … More ted within 200 G. More uniform field will be, furthermore, accomplished by sorting of permanent magnets. The height of the wiggler of only 75 mm means one of the smallest microwiggler in the world. This wiggler also interested some researchers in short wavelength SASEFEL and gamma-gamma collider besides FIR FEL.In the field emission experiment, conventional tungsten wire was electrolytically etched to a needle for investigation. It was found from simulation and experiment that electron beam current was enlarged in a certain voltage range of 2nd gate depending on the cathode potential and the distance between 1st and 2nd gates. Four tungsten needles could be well arrayed. Bunched carbon nanotubes were also supplied to field emission source research. We could attain very high field emission current of 2.2 mA which is 〜100 times as high as that of W tip. The current fluctuation is also very small <4%. It would be said that our nanotubes have necessary properties for Cherenkov FEL or Smith-Purcell FEL at present time.Further studies are in progress to propagate the electron beam into the wiggler and emit the radiation. Less