Research on Small Sized Free Electron Laser Using Hybrid Helical Microwiggler

点击翻译按钮获取中文摘要

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