As a natural character of high gain flee electron laser (FEL),harmonic radiation is regarded as the natural extensions to short wavelengths.In high gain harmonic generation (HGHG) scheme,harmonic evolution may be attr...As a natural character of high gain flee electron laser (FEL),harmonic radiation is regarded as the natural extensions to short wavelengths.In high gain harmonic generation (HGHG) scheme,harmonic evolution may be attributed to the initial harmonic bunching,self amplification of the harmonic radiation,electron beam strongly bunched by the fundamental radiation,the faster longitudinal dynamics and the fundamental synchrotron oscillation.It is more complex than harmonic evolution in other FEL schemes.In this paper,via theoretical analyses and three dimensional simulations,a general description of different aspects of harmonic evolution in the HGHG process is presented.展开更多
Cascading stages of high-gain harmonic generation(HGHG) free electron laser(FEL) is a promising way to produce fully coherent X-ray radiation.As a test facility for modern FEL R&D,the Shanghai deep ultraviolet FEL...Cascading stages of high-gain harmonic generation(HGHG) free electron laser(FEL) is a promising way to produce fully coherent X-ray radiation.As a test facility for modern FEL R&D,the Shanghai deep ultraviolet FEL(SDUV-FEL) is now under upgrading for the cascading two stages of HGHG experiment.Since the energy of the electron beam is as low as about 185 MeV after upgrade,the total harmonic number of this two stages HGHG is only 2×2,and the wavelength of the final radiation is 196.5 nm which is the 4th harmonic of the 786 nm seed laser.With help of three-dimensional simulation codes,design studies on the FEL physics for the cascaded HGHG experiment are present based on the parameters of the upgraded SDUV-FEL facility.It is found from the simulation results that the part of the electron beam which has been used in the first stage can still generate powerful radiation in the radiator of the second stage,and this radiation will be difficult to be separated from the radiation generated by the fresh part of the electron beam.To overcome this problem,a novel method based on the energy spectrum of the electron beam is proposed in this paper to demonstrate the "fresh bunch" technique.展开更多
By choosing parameters in the modulator, the dispersive section and the seed laser, the spatial bunching of the electron beam can be correlated to the n-th harmonic of the radiator radiation, instead of the fundamenta...By choosing parameters in the modulator, the dispersive section and the seed laser, the spatial bunching of the electron beam can be correlated to the n-th harmonic of the radiator radiation, instead of the fundamental radiation in conventional high-gain harmonic generation (HGHG). Thus, the radiator undulator is operated at high harmonic mode. In this paper, the possibility of harmonic operation of Shanghai deep ultraviolet (SDUV) free electron laser (FEL) is studied. Discussions on the principle of harmonic operation, the simulation code development, the simulation results, and the proposed experimental procedure for verification of harmonic operation at the SDUV FEL are also presented.展开更多
Using the recently proposed echo-enabled harmonic generation （EEHG） free-electron laser （FEL） scheme, it is shown that operating the Shanghai deep ultraviolet FEL （SDUV-FEL） with single-stage to higher harmonics...Using the recently proposed echo-enabled harmonic generation （EEHG） free-electron laser （FEL） scheme, it is shown that operating the Shanghai deep ultraviolet FEL （SDUV-FEL） with single-stage to higher harmonics is very promising, with higher frequency up-conversion effciency, higher harmonic selectivity and lower power requirement of the seed laser. The considerations on a proof-of-principle experiment and expected performance in SDUV-FEL are given.展开更多
Cascading stages of high gain harmonic generation free electron laser （FEL） seem to be a feasible way to generate short wavelength radiation. With help of the analytical estimates, we design a two-stage cascading sc...Cascading stages of high gain harmonic generation free electron laser （FEL） seem to be a feasible way to generate short wavelength radiation. With help of the analytical estimates, we design a two-stage cascading scheme to achieve 131 nm DUV radiation on the basis of the Shanghai deep ultraviolet free electron laser test facility. Detailed studies on the FEL performance, the stability and the sensitivity of the output power to parameter variation have been achieved by GENESIS1.3, and design of the lattice structure is presented.展开更多
In high gain harmonic generation （HGHG） free electron laser （FEL）, with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of th...In high gain harmonic generation （HGHG） free electron laser （FEL）, with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation （HO） mode. In this paper, we investigate HO of HGHG FEL. Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy.展开更多
We study a self-seeded high-gain harmonic generation（HGHG） free-electron laser（FEL） scheme to extend the wavelength of a soft X-ray FEL. This scheme uses a regular self-seeding monochromator to generate a seed las...We study a self-seeded high-gain harmonic generation（HGHG） free-electron laser（FEL） scheme to extend the wavelength of a soft X-ray FEL. This scheme uses a regular self-seeding monochromator to generate a seed laser at the wavelength of 1.52 nm, followed by a HGHG configuration to produce coherent, narrow-bandwidth harmonic radiations at the GW level. The 2nd and 3rd harmonic radiation is investigated with start-to-end simulations.Detailed studies of the FEL performance and shot-to-shot fluctuations are presented.展开更多
基金supported by the Key Project for Promoting Fundamental Research in China (Grant No.2002CB713600)
文摘As a natural character of high gain flee electron laser (FEL),harmonic radiation is regarded as the natural extensions to short wavelengths.In high gain harmonic generation (HGHG) scheme,harmonic evolution may be attributed to the initial harmonic bunching,self amplification of the harmonic radiation,electron beam strongly bunched by the fundamental radiation,the faster longitudinal dynamics and the fundamental synchrotron oscillation.It is more complex than harmonic evolution in other FEL schemes.In this paper,via theoretical analyses and three dimensional simulations,a general description of different aspects of harmonic evolution in the HGHG process is presented.
基金supported by the National Natural Science Foundation of China (10935011)the National Basic Research Program of China (2011CB808300)
文摘Cascading stages of high-gain harmonic generation(HGHG) free electron laser(FEL) is a promising way to produce fully coherent X-ray radiation.As a test facility for modern FEL R&D,the Shanghai deep ultraviolet FEL(SDUV-FEL) is now under upgrading for the cascading two stages of HGHG experiment.Since the energy of the electron beam is as low as about 185 MeV after upgrade,the total harmonic number of this two stages HGHG is only 2×2,and the wavelength of the final radiation is 196.5 nm which is the 4th harmonic of the 786 nm seed laser.With help of three-dimensional simulation codes,design studies on the FEL physics for the cascaded HGHG experiment are present based on the parameters of the upgraded SDUV-FEL facility.It is found from the simulation results that the part of the electron beam which has been used in the first stage can still generate powerful radiation in the radiator of the second stage,and this radiation will be difficult to be separated from the radiation generated by the fresh part of the electron beam.To overcome this problem,a novel method based on the energy spectrum of the electron beam is proposed in this paper to demonstrate the "fresh bunch" technique.
基金Key Project for Promoting Fundamental Research in China (Grant No. 2002CB713600)
文摘By choosing parameters in the modulator, the dispersive section and the seed laser, the spatial bunching of the electron beam can be correlated to the n-th harmonic of the radiator radiation, instead of the fundamental radiation in conventional high-gain harmonic generation (HGHG). Thus, the radiator undulator is operated at high harmonic mode. In this paper, the possibility of harmonic operation of Shanghai deep ultraviolet (SDUV) free electron laser (FEL) is studied. Discussions on the principle of harmonic operation, the simulation code development, the simulation results, and the proposed experimental procedure for verification of harmonic operation at the SDUV FEL are also presented.
基金Supported by Major State Basic Research Development Program of China (2002CB713600)
文摘Using the recently proposed echo-enabled harmonic generation （EEHG） free-electron laser （FEL） scheme, it is shown that operating the Shanghai deep ultraviolet FEL （SDUV-FEL） with single-stage to higher harmonics is very promising, with higher frequency up-conversion effciency, higher harmonic selectivity and lower power requirement of the seed laser. The considerations on a proof-of-principle experiment and expected performance in SDUV-FEL are given.
基金Supported by Major State Basic Research Development Program of China(2002CB713600)
文摘Cascading stages of high gain harmonic generation free electron laser （FEL） seem to be a feasible way to generate short wavelength radiation. With help of the analytical estimates, we design a two-stage cascading scheme to achieve 131 nm DUV radiation on the basis of the Shanghai deep ultraviolet free electron laser test facility. Detailed studies on the FEL performance, the stability and the sensitivity of the output power to parameter variation have been achieved by GENESIS1.3, and design of the lattice structure is presented.
基金Supported by Major State Basic Research Development Program of China(2002CB713600)
文摘In high gain harmonic generation （HGHG） free electron laser （FEL）, with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation （HO） mode. In this paper, we investigate HO of HGHG FEL. Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy.
文摘We study a self-seeded high-gain harmonic generation（HGHG） free-electron laser（FEL） scheme to extend the wavelength of a soft X-ray FEL. This scheme uses a regular self-seeding monochromator to generate a seed laser at the wavelength of 1.52 nm, followed by a HGHG configuration to produce coherent, narrow-bandwidth harmonic radiations at the GW level. The 2nd and 3rd harmonic radiation is investigated with start-to-end simulations.Detailed studies of the FEL performance and shot-to-shot fluctuations are presented.
