Radiation Mechanism Study Of Storage Ring Light Sources And Free Electron Lasers

The storage ring based light source is mature and reliable,which can generate picosecond-scale radiation pulses from infrared to hard X-ray to study the material structure from the molecule scale to the atomic scale.It has high stability,high repetition rate and availability of multiple beamlines.Linear accelerator based free-electron laser(FEL)is used to generate radiation pulses with short wavelengths,high peak brightness,high coherence,and ultrafast resolution.Generating high-order harmonics of the seed laser and strong coherent radiation in the storage ring has been of great interest in the accelerator based light source community.Therefore,it is inevitable to combine the FEL operating mechanisms with the storage rings.The operating mechanism of FEL is the core of FEL physics.There are already a variety of operating mechanisms,the most typical of which is the self-amplified spontaneous emission(SASE).SASE-FEL has the ability to provide extremely high intense,ultra-short light pulses with excellent spatial coherence.However,since the spontaneous radiation originates from the beam instability,SASE usually has poor temporal coherence,large shot-to-shot power fluctuations and relatively long undulator saturation length.Frequency up-conversion schemes can significantly improve the temporal coherence of SASE-FEL and suppress power jitter.These schemes include high-gain harmonic generation(HGHG),the echo-enabled harmonic generation(EEHG)and phase-merging enhanced harmonic generation(PEHG),in which HGHG and EEHG have been experimentally demonstrated.However,these schemes rely on the relatively large laser-induced energy modulation to achieve high harmonic bunching,which is not preferred in storage rings.Therefore,it is indispensable to propose novel radiation mechanisms to improve these mechanisms and meet the increasing demands of advanced light source users.In this context,this thesis first studies the interaction of obliquely incident laser and electron beam in the undulator,which is a basic and important physical process in the frequency up-conversion FEL schemes and there is no relevant work to study this process according to the author's knowledge.This article systematically studies this physical process for the first time.Theoretical analysis and numerical simulations demonstrate that this interaction will not only introduce energy modulation but also angle modulation on the electron beam phase space.This will reduce the harmonic conversion e ciency of the frequency up-conversion schemes(such as HGHG and EEHG)and slightly increase the emittance of the electron beam.At the same time,the interaction can also be regarded as a novel multi-dimensional beam manipulation technique(oblique laser modulation tech,OLMT).OLMT can partially transfer the energy modulation dependence required for generating high harmonics in the traditional scheme to the angle modulation dependence,thereby reducing the desired energy modulation depth of the electron beam to generate high harmonic bunching.Based on this,two novel schemes using OLMT are proposed to achieve frequency up-conversion in storage rings,the second of which is more worthy of admiration.With a simple setup of a short modulator and a dipole magnet,this scheme cleverly correlates the harmonic bunching with the angular divergence of the electron beam.With the fact that the angular divergence in the vertical direction in the storage ring is small,this tech enhances the harmonic bunching of the electron beam with a very small laserinduced energy.Numerical simulations show that this scheme could generate hundreds of megawatts,fully coherent EUV radiation pulses through a ten-meter long radiator in a di raction limit storage ring.Compared with other frequency up-conversion schemes,this scheme has higher harmonic conversion e ciency;compared with the SASE-FEL based on storage ring,this scheme could substantially reduce the radiation saturation length while basically maintaining the FEL peak power.The lattice setting of the proposed scheme is very simple and feasible in existing facilities.The proposed scheme provides a new technical route for the realization of EUV and soft X-ray FEL in storage rings.OLMT can also be used in emittance exchange(EEX).EEX can rearrange the distribution of electron beam and is widely used in storage rings,FEL and colliders.A novel EEX scheme based on OLMT is porposed to achieve EEX of the electron beam on the optical laser wavelength scale.Theoretical research shows that this scheme could greatly improve the performance of FEL,and could achieve bunch shaping on the optical wavelength scale.The proposed scheme makes a breakthrough to the traditional EEX scheme and has an important enlightening significance for the theoretical exploration and experimental research of future EEX.It has broad application potential in the fields of storage rings and FEL.