The Research Of Transverse Gradient Undulator

Free electron laser is a new generation of coherent radiation of strong source, which can make electromagnetic radiation of free electron stimulated and amplificated. Free electron laser can operate in the band where normal laser can not reach, and it has high peak brightness, continuously tunable wavelength, wide operating range, high power, high efficiency, good radiation coherence and controllable time structure, which has been a hot spot of domestic and international researches in recent years. And the undulator is a core component of free electron laser, which provide periodic transverse static magnetic field for the interaction between the electronic and optical field.In this context, this paper starts around the undulator. According to the actual demand, this paper is mainly on two main studies which are the transverse gradient undulator and the focusing undulator.In this paper, we reviewed and summarized the basic principles and the development trend of free electron laser, as well as the physical properties of undulators. What’s more, we introduced some background of this subject and some related numerical simulation softwares.We studied on the transverse gradient undulator which can be used for large energy spread of electron beams. Classic transverse gradient undulators usually make the surface of magnetic poles and blocks of undulators angled, to obtain a magnetic field of transverse gradient. In this paper, we designed a new structure of magnets and poles by tilting the back surface of the magnets and poles or making the surface of magnets and poles wedged and so on. We proposed some new schemes of transverse gradient undulators. At the same time, we analyzed and calculated the impact of the inclination angle of the magnets and poles of different schemes on the transverse gradient, and compared the transverse gradient of different schemes changing with the ratio of gap and period. The results showed that, the methods of tilting the back surface of the magnets and poles or making the surface of magnets and poles wedged can apply the transverse gradient. If we make the black surface of magnets or poles angled based on inclined poles or wedged undulators, we can get greater transverse gradient. In addition, we analyzed the applicable scope of transverse gradient undulators. We also use B2E software to calculate the deflecting effect of electron beams.We studied on the transverse focusing undulators which can be used for low energy of electron beams and the situation of smaller β function. We discussed several transverse focusing undulators by changing geometry of magnets and poles. These programs are based on alternating inclined magnets and the poles to produce transverse gradient fields for focusing the electron beam. We used RADIA software to simulate the transverse magnetic field of undulators of different structures respectively, and analyzed the changing of the transverse focusing characteristic, and then compared them with each other. The results showed that, one scheme have the optimal focusing gradient, which has inclined surface of magnets and poles, and the magnets around the pole are asymmetric. If we tilt the back surface of poles at the same time, it will has stronger focusing gradient. We selected the transverse focusing undulator of the best characteristics, and studied the influence of the main parameters for the focusing characteristics in detail. In addition, this structure of transverse focusing undulator is more simple and easier to manufacture. Finally, according to the results of the existing data, we obtained some meaningful conclusions.