X-ray free-electron lasers(XFELs)can generate bright X-ray pulses with short durations and narrow bandwidths,leading to extensive applica-tions in many disciplines such as biology,materials science,and ultrafast scien...X-ray free-electron lasers(XFELs)can generate bright X-ray pulses with short durations and narrow bandwidths,leading to extensive applica-tions in many disciplines such as biology,materials science,and ultrafast science.Recently,there has been a growing demand for X-ray pulses with high photon energy,especially from developments in“diffraction-before-destruction”applications and in dynamic mesoscale materials science.Here,we propose utilizing the electron beams at XFELs to drive a meter-scale two-bunch plasma wakefield accelerator and double the energy of the accelerated beam in a compact and inexpensive way.Particle-in-cell simulations are performed to study the beam quality degradation under different beam loading scenarios and nonideal issues,and the results show that more than half of the accelerated beam can meet the requirements of XFELs.After its transport to the undulator,the accelerated beam can improve the photon energy to 22 keV by a factor of around four while maintaining the peak power,thus offering a promising pathway toward high-photon-energy XFELs.展开更多
X射线作为一种探测原子尺度物质结构的重要工具,已广泛应用于前沿科学研究、医疗诊断、工业检测等领域。X射线自由电子激光器(X-ray free electron laser,XFEL)作为目前世界上最先进的光源之一,以其超高峰值亮度、飞秒级脉冲和全相干特...X射线作为一种探测原子尺度物质结构的重要工具,已广泛应用于前沿科学研究、医疗诊断、工业检测等领域。X射线自由电子激光器(X-ray free electron laser,XFEL)作为目前世界上最先进的光源之一,以其超高峰值亮度、飞秒级脉冲和全相干特性极大推动了X射线技术的发展与应用。全球众多国家和研究机构正积极推进XFEL设施的建设与技术进步。该文论述了XFEL的基本原理、国际上的研究进展与最新技术突破,以及我国在XFEL技术方面的研究进展,并对我国未来的XFEL技术进行了展望。展开更多
Fe-based layer with Ti（CxN1-x） particulates on Adamite roller surface was obtained by a 5 kW traverse-flowing CO2 laser cladding technology. The microstructures of the layer were detected by optical microscopy （OM...Fe-based layer with Ti（CxN1-x） particulates on Adamite roller surface was obtained by a 5 kW traverse-flowing CO2 laser cladding technology. The microstructures of the layer were detected by optical microscopy （OM）,X-ray diffraction （XRD）,scanning electron microscopy （SEM）,and electron probe microscopy analysis （EMPA）. The tests of wear resistance was carried out on the test machine. It was seen that a good metallurgical bonding between the coating and the substrate was achieved. The microstructure contains bulky dendritic crystal and small size Ti（CxN1-x） grains that are uniformly distributed in the solid solution matrix. The wear tests showed that the laser coating provided an excellent wear resistance property at room temperature.展开更多
In most collisional schemes of x-ray laser （XRL） experiments, a bow-like intensity distribution of XRL is often observed, and it is generally ascribed to the two-dimensional hydrodynamic behaviour of expanding plasm...In most collisional schemes of x-ray laser （XRL） experiments, a bow-like intensity distribution of XRL is often observed, and it is generally ascribed to the two-dimensional hydrodynamic behaviour of expanding plasma. In order to better understand its essence in physics, a newly developed two-dimensional non-equilibrium radiation hydrodynamic code XRL2D is used to simulate a quasi-steady state Ni-like Ag XRL experiment on ShenGuang-Ⅱfacility. The simulation results show that the bow-like distribution of Ni-like ions caused by over-ionization in the central area of plasma is responsible for the bow-like shape of the XRL intensity distribution observed.展开更多
The Ni-like Ag 13.9 nm x-ray laser has been previously demonstrated that the higher gain near critical surface contributes little to the amplification of the x-ray laser because of severe refraction. In this paper, th...The Ni-like Ag 13.9 nm x-ray laser has been previously demonstrated that the higher gain near critical surface contributes little to the amplification of the x-ray laser because of severe refraction. In this paper, the transient collision excitation （TCE） Ni-like Ag 13.9 nm x-ray laser is simulated, driven by two 3 ps short pulse preceded by a 330 ps long prepulse, optimization of the peak to peak delay time of the two short pulses is made to get the best results. Simulation indicates that by producing lowly ionized preplasma with smoothly varying electron density, it is possible to decrease electron density gradient in higher density region, and thus higher gains near this region could be utilized, and if the main short pulse is delayed by 900ps, local gains where electron density larger than - 4 × 10^20 cm^-3 could be utilized.展开更多
基金supported by the National Grand Instrument Project No. SQ2019YFF01014400the Natural Science Foundation of China (Grant Nos. 12375147, 12435011, 12075030)+2 种基金the Beijing Outstanding Young Scientist Project, Project for Young Scientists in Basic Research of Chinese Academy of Sciences (YSBR-115)the Beijing Normal University Scientific Research Initiation Fund for Introducing Talents No. 310432104the Fundamental Research Funds for the Central Universities, Peking University
文摘X-ray free-electron lasers(XFELs)can generate bright X-ray pulses with short durations and narrow bandwidths,leading to extensive applica-tions in many disciplines such as biology,materials science,and ultrafast science.Recently,there has been a growing demand for X-ray pulses with high photon energy,especially from developments in“diffraction-before-destruction”applications and in dynamic mesoscale materials science.Here,we propose utilizing the electron beams at XFELs to drive a meter-scale two-bunch plasma wakefield accelerator and double the energy of the accelerated beam in a compact and inexpensive way.Particle-in-cell simulations are performed to study the beam quality degradation under different beam loading scenarios and nonideal issues,and the results show that more than half of the accelerated beam can meet the requirements of XFELs.After its transport to the undulator,the accelerated beam can improve the photon energy to 22 keV by a factor of around four while maintaining the peak power,thus offering a promising pathway toward high-photon-energy XFELs.
文摘X射线作为一种探测原子尺度物质结构的重要工具,已广泛应用于前沿科学研究、医疗诊断、工业检测等领域。X射线自由电子激光器(X-ray free electron laser,XFEL)作为目前世界上最先进的光源之一,以其超高峰值亮度、飞秒级脉冲和全相干特性极大推动了X射线技术的发展与应用。全球众多国家和研究机构正积极推进XFEL设施的建设与技术进步。该文论述了XFEL的基本原理、国际上的研究进展与最新技术突破,以及我国在XFEL技术方面的研究进展,并对我国未来的XFEL技术进行了展望。
基金Sponsored by Shandong Natural Science Foundation of China (Z2006F07)
文摘Fe-based layer with Ti（CxN1-x） particulates on Adamite roller surface was obtained by a 5 kW traverse-flowing CO2 laser cladding technology. The microstructures of the layer were detected by optical microscopy （OM）,X-ray diffraction （XRD）,scanning electron microscopy （SEM）,and electron probe microscopy analysis （EMPA）. The tests of wear resistance was carried out on the test machine. It was seen that a good metallurgical bonding between the coating and the substrate was achieved. The microstructure contains bulky dendritic crystal and small size Ti（CxN1-x） grains that are uniformly distributed in the solid solution matrix. The wear tests showed that the laser coating provided an excellent wear resistance property at room temperature.
文摘In most collisional schemes of x-ray laser （XRL） experiments, a bow-like intensity distribution of XRL is often observed, and it is generally ascribed to the two-dimensional hydrodynamic behaviour of expanding plasma. In order to better understand its essence in physics, a newly developed two-dimensional non-equilibrium radiation hydrodynamic code XRL2D is used to simulate a quasi-steady state Ni-like Ag XRL experiment on ShenGuang-Ⅱfacility. The simulation results show that the bow-like distribution of Ni-like ions caused by over-ionization in the central area of plasma is responsible for the bow-like shape of the XRL intensity distribution observed.
文摘The Ni-like Ag 13.9 nm x-ray laser has been previously demonstrated that the higher gain near critical surface contributes little to the amplification of the x-ray laser because of severe refraction. In this paper, the transient collision excitation （TCE） Ni-like Ag 13.9 nm x-ray laser is simulated, driven by two 3 ps short pulse preceded by a 330 ps long prepulse, optimization of the peak to peak delay time of the two short pulses is made to get the best results. Simulation indicates that by producing lowly ionized preplasma with smoothly varying electron density, it is possible to decrease electron density gradient in higher density region, and thus higher gains near this region could be utilized, and if the main short pulse is delayed by 900ps, local gains where electron density larger than - 4 × 10^20 cm^-3 could be utilized.
