Search On Especial Undulators In Synchrotron Radiation Source And Free Electron Laser

Review the development history of the synchrotron radiation source, we could find that while the undulators are widely used as the insert devices, the brilliance of SR has been greatly raised and the spectral range has been widened more efficient. Free Electron Laser (FEL) is the most promising fourth-generation source and has unique characteristics, such as adjustable wavelength, high power and coherent radiation, etc. Therefore, FEL becomes one of research hotspots around world. Furthermore, undulator as a key equipment of FEL, receives the widespread attention.In order to improve the output power, the feasibility of using variable parameter undulator in FEL Oscillator based on electrostatic accelerator was systematically studied. Firstly, the paper gave the design of Terahertz FEL Oscillator based on electrostatic accelerator, and the influence of the parameters of the resonant on FEL performance was also studied. Based on those results, though both theoretical analyses and numerical simulation, we investigated the influence of the variable parameter undulator on the saturated power and time of FEL Oscillator. The results demonstrated that using the positive variable parameter undulator with proper taper could improve the saturated power. Moreover, we also analyzed the FEL Oscillator employed inverse variable parameter undulator.We introduced the basic theory of current quasi-periodic undulator (QPU) and the typical structures were summarized. The relationship between the harmonic radiation and the thickness of V-magnets (blocks magnetized vertically) in the pure permanent magnet undulator was analyzed. Based on above analysis, we proposed some new schemes of QPU:Modified udnualtor, Modified QPU and New QPU. The radiation spectral fluxes of these schemes are numerically calculated and compared with those of the standard undulator and the current QPU. The results demonstrate that new schemes of QPU can greatly suppress the high-order harmonic radiation comparing with the current QPU. Moreover, the new QPU scheme is suited to in-vacuum undulator owing to its smooth face of the magnet pole. Therefor, Modified QPU is under construction for renovation project of the NSRL. Then, the harmonics suppression effect of QPUs in SASE FEL is also investigated. The numerical calculations showed that if the fraction of QPUs and its offgap are appropriate in undulators system, the harmonics radiation could be suppressed remarkably, meanwhile the fundamental saturation length increases not too much.High-field hybrid is of great importance to realize the miniaturized FEL equipments and extend the FEL radiation to shorter wavelengths. We optimized the parameters of two existing schemes of hybrid with pole has edge-added magnets and hybrid with wedge-shape pole. Their magnetic fields were contrasted. Next, a new hybrid which wedge-shape pole has edge-added magnets was proposed. We calculated the peak field and harmonic fields of each scheme when changing the ratio of gap and period length of undulator. From the results, we could find that when the ratio of gap and period length was larger than0.3, the new scheme could increase the peak field and harmonic filed of hybrid effectively.