Coherent motion of particles in a plasma can imprint itself on radiation.The recent advent of high-power lasers—allowing the nonlinear inverse Compton-scattering regime to be reached—has opened the possibility of lo...Coherent motion of particles in a plasma can imprint itself on radiation.The recent advent of high-power lasers—allowing the nonlinear inverse Compton-scattering regime to be reached—has opened the possibility of looking at collective effects in laser–plasma interactions.Under certain conditions,the collective interaction of many electrons with a laser pulse can generate coherent radiation in the hard x-ray regime.This perspective paper explains the limitations under which such a regime might be attained.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
For experiments such as on Ni-like Ag x-ray laser, driven by 1ω laser, the gain region is only several nm depth near the target surface, this paper proposes a new two-layer target, in which a thin layer (several nm ...For experiments such as on Ni-like Ag x-ray laser, driven by 1ω laser, the gain region is only several nm depth near the target surface, this paper proposes a new two-layer target, in which a thin layer (several nm depth) of silver is plated on the surface of some other materials. Furthermore, the Ni-like Ag 13.9 nm x-ray laser produced by three new kinds of two-layer target with CH, Al and Ge as foundation, was theoretically studied.展开更多
Based on the two-dimensional model, this paper compares the hydrodynamics of slab x-ray laser plasma produced by different nonuniform line focused irradiations. It finds that the average intensity and the duration of ...Based on the two-dimensional model, this paper compares the hydrodynamics of slab x-ray laser plasma produced by different nonuniform line focused irradiations. It finds that the average intensity and the duration of laser pulse and the overall shape of the intensity distribution in the focal line have different influences on the plasma. Calculations show that the evolution of temperature variation is more sensitive to the pulse duration and the electron density variation is more sensitive to the pulse intensity. Pulses with duration of 200 ps to 500 ps and with intensity of 0.2 TW/cm2 to 1.0 TW/cm2 are proved acceptable in slab x-ray lasers.展开更多
We investigate the Ne-like Cr x-ray laser at 28.6 nm by using a modified ID lagrangian hydrodynamic code MEDI03 coupled with an atomic physics data package and a 2D ray tracing code as a post-processor. The laser pump...We investigate the Ne-like Cr x-ray laser at 28.6 nm by using a modified ID lagrangian hydrodynamic code MEDI03 coupled with an atomic physics data package and a 2D ray tracing code as a post-processor. The laser pumping configuration includes two prepulses and one main pulse. The first prepulse normally irradiates the target, while the second prepulse and the main pulse irradiate the target at grazing-incident angles. We predict that saturation can be achieved for the Ne-like Cr x-ray lasers with a total pumping energy of 125mJ, Good beam qualities with no deflecting angle and a small divergence angle of 5 mrad are observed.展开更多
A method of studying a non-equilibrium x-ray laser plasma is developed by extending the existing one-dimensional similarity equations to the case of two-dimensional plasma study in the directions perpendicular to the ...A method of studying a non-equilibrium x-ray laser plasma is developed by extending the existing one-dimensional similarity equations to the case of two-dimensional plasma study in the directions perpendicular to the slab and along a focal line. With this method the characteristics of pre-plasma are optimized for transient neon-like Cr x-ray laser. It is found that when the duration and the intensity of 1.053μm pre-pulse are 1.2 ns and 6.5 TW/cm^2 respectively with a delay time of 1.5 ns, the temperature and the temperature discrepancy each approach a proper state, which will provide a uniform distribution of properly ionized neon-like Cr ions before the arrival of pumping pulse.展开更多
Using an X-ray free electron laser(XFEL)at 960 eV to photo-ionize the 1s electron in neutral neon followed by lasing on the 2p-1s transition in singly-ionized neon,an inner-shell X-ray laser was demonstrated at 849 eV...Using an X-ray free electron laser(XFEL)at 960 eV to photo-ionize the 1s electron in neutral neon followed by lasing on the 2p-1s transition in singly-ionized neon,an inner-shell X-ray laser was demonstrated at 849 eV in singly-ionized neon gas several years ago.It took decades to demonstrate this scheme,because it required a very strong X-ray source that could photo-ionize the 1s(K shell)electron in neon on a timescale comparable to the intrinsic Auger lifetime in neon of 2 fs.In this paper,we model the neon inner shell X-ray laser under similar conditions to those used in the XFEL experiments at the SLAC Linac Coherent Light Source(LCLS),and show how we can improve the efficiency of the neon laser and reduce the drive requirements by tuning the XFEL to the 1s-3p transition in neutral neon in order to create gain on the 2p-1s line in neutral neon.We also show how the XFEL could be used to photo-ionize L-shell electrons to drive gain on n=3-2 transitions in singlyionized Ar and Cu plasmas.These bright,coherent,and monochromatic X-ray lasers may prove very useful for doing high-resolution spectroscopy and for studying non-linear process in the X-ray regime.展开更多
A simple modified model is presented based on R. A. London's self-similarity model on time-independent ionization hydrodynamics of exploding foil X-ray lasers. In our model, the time-dependent ionization effect is un...A simple modified model is presented based on R. A. London's self-similarity model on time-independent ionization hydrodynamics of exploding foil X-ray lasers. In our model, the time-dependent ionization effect is under consideration and the average ion charge depends on the temperature. Then we obtain the new scaling laws for temperature, scale length and electron density, which have better agreement with experimental results.展开更多
Gain coefficients are calculated for neon-like gallium and germanium ions. Shorter wavelengths are calculated and predicted to be emitted. The gain coefficients are calculated among 457 energy levels of the neon-like ...Gain coefficients are calculated for neon-like gallium and germanium ions. Shorter wavelengths are calculated and predicted to be emitted. The gain coefficients are calculated among 457 energy levels of the neon-like ions. Collisional excitations were calculated through the distorted wave approximations through five electron temperatures T<sub>e</sub> = 300, 500, 700, 1000 and 1500 eV.展开更多
AmpliHcation of spontaneous emissions at 19.6,23.2 and 23.6 nm have been observed by a “ultiple-Target Series Coupling”design in Ge plasma,.The combined length for four targets is up to 56mm.The gain length product(...AmpliHcation of spontaneous emissions at 19.6,23.2 and 23.6 nm have been observed by a “ultiple-Target Series Coupling”design in Ge plasma,.The combined length for four targets is up to 56mm.The gain length product(GL)of small signal is up to 18 for both lines at 23.2 and 23.6 nmt and the effective GL is 16.4 and 15.7 for these two lines respectively.This two lines are obviously tending to saturation.The divergence of x-ray laser beam is about 4 mrad.展开更多
An x-ray laser shadowgraphy experiment was conducted on Xingguang-Ⅱ laser facility in 1996.A multi-layer spherical mirror was used as an imaging element and a high sensitivity CCD camera as a detector.We measured the...An x-ray laser shadowgraphy experiment was conducted on Xingguang-Ⅱ laser facility in 1996.A multi-layer spherical mirror was used as an imaging element and a high sensitivity CCD camera as a detector.We measured the near-field image of the Ti x-ray laser beam.With a Ti x-ray laser beam as a backlight source,we obtained a clear CU mesh image,demonstrating the potential as advanced diagnostic measurements to study high density plasmas in inertial confinement fusion research.展开更多
Corrigendum text:There is a misprint in the text of Figs.3 and 4.The text on the bottom part of Figs.3 and 4 should be“100 fs pulse Photoexcitation”and“1 fs pulse Photoexcitation”respectively.This error does not a...Corrigendum text:There is a misprint in the text of Figs.3 and 4.The text on the bottom part of Figs.3 and 4 should be“100 fs pulse Photoexcitation”and“1 fs pulse Photoexcitation”respectively.This error does not affect any conclusions in this work,and it has been corrected in the printed version of the journal.展开更多
Advances in X-ray laser sources have paved the way to relativistic attosecond X-ray laser pulses and opened up the possibility of exploring highenergy-density physics with this technology.With particle-in-cell simulat...Advances in X-ray laser sources have paved the way to relativistic attosecond X-ray laser pulses and opened up the possibility of exploring highenergy-density physics with this technology.With particle-in-cell simulations,we investigate the interaction of realistic metal crystals with relativistic X-ray laser pulses of parameters that will be available in the near future.A wakefield of the order of TV/cm is excited in the crystal and accelerates trapped electrons stably even though the wakefield is locally modulated by the crystal lattice.Electron injection either occurs at the sharp crystal-vacuum boundary or is controlled by coating the crystal with a high-density film.High-repetition-rate attosecond(20 as)monoenergetic electron beams of energy 125 MeV,charge 100 fC,and emittance 1.6310−9mrad can be produced by shining MHz X-ray laser pulses of energy 2.1 mJ onto coated crystals several micrometers thick.Such a miniature crystal accelerator,which has high reproducibility and allows sufficient control of the parameters of the electron beams,greatly expands the applications of X-ray free electron lasers.For example,it could serve as an ideal electron source for ultrafast electron diffraction and ultrafast electron microscopy to achieve attosecond resolution.展开更多
A new type of soft X-ray source, i.e. a plasma-based X-ray laser, is found to be promising to conduct transient measurement. By means of picosecond X-ray laser speckles, the dynamic microscopic polarization clusters w...A new type of soft X-ray source, i.e. a plasma-based X-ray laser, is found to be promising to conduct transient measurement. By means of picosecond X-ray laser speckles, the dynamic microscopic polarization clusters within cubic (paraelectric) BaTiO3 was directly observed and characterized in a microscopic scale for the first time. This opens a way to study this type of clusters, which usually manifest large external-field response for ferroelectric materials.展开更多
Monochromatic x-ray imaging is an essential method for plasma diagnostics related to density information.Large-field high-resolution monochromatic imaging of a He-like iron(Fe XXV)Kαcharacteristic line(6.701 keV)for ...Monochromatic x-ray imaging is an essential method for plasma diagnostics related to density information.Large-field high-resolution monochromatic imaging of a He-like iron(Fe XXV)Kαcharacteristic line(6.701 keV)for laser plasma diagnostics was achieved using a developed toroidal crystal x-ray imager.A high-index crystal orientation Ge(531)wafer with a Bragg angle of 75.37°and the toroidal substrate were selected to obtain sufficient diffraction efficiency and compensate for astigmatism under oblique incidence.A precise offline assembly method of the toroidal crystal imager based on energy substitution was proposed,and a spatial resolution of 3-7μm was obtained by toroidal crystal imaging of a 600 line-pairs/inch Au grid within an object field of view larger than 1.0 mm.The toroidal crystal x-ray imager has been successfully tested via side-on backlight imaging experiments of the sinusoidal modulation target and a 1000 line-pairs/inch Au grid with a linewidth of 5μm using an online alignment method based on dual positioning balls to indicate the target and backlighter.This paper describes the optical design,adjustment method,and experimental results of a toroidal crystal system in a laboratory and laser facility.展开更多
The generation of hollow atoms will reduce the probability of light absorption and provide a high-quality diffraction image in the experiment. In this paper, we calculated the ionization rate of the Kr atom under x-ra...The generation of hollow atoms will reduce the probability of light absorption and provide a high-quality diffraction image in the experiment. In this paper, we calculated the ionization rate of the Kr atom under x-ray free-electron laser(XFEL) using Hartree–Fock–Slater model and simulated the ionization model of Kr atom using Monte–Carlo method to determine the response of the hollow atom of Kr atom to the XFEL photon energy. Calculating the correlation between the total photoionization cross-section of the ground state of Kr atom and the photon energy, we determined three particular photon energies of 1.75 ke V, 1.90 ke V, and 14.30 ke V. The dynamics simulation under the experimental condition's17.50 ke V photon energy was achieved by implementing the Monte–Carlo method and calibrating the photon flux modeling parameters. Consequently, our calculated data are more consistent with experimental phenomena than previous theoretical studies. The saturable absorption of Kr at 1.75 ke V, 1.90 ke V, 14.30 ke V, and 17.50 ke V energies was further investigated by using the optimized photon flux model theory. We compared the statistics on main ionization paths under those four specific photon energies and calculated the population changes of various Kr hollow atoms with different configurations.The results demonstrate that the population of hollow atoms produced at the critical ionization photon energy is high. Furthermore, the change of population with respect to position is smooth, which shows a significant difference between the generation mode of ions with low and high photon energies. The result is important for the study of medium-and high-Z element hollow atoms, which has substantial implications for the study of hollow atoms with medium and high charge states, as well as for the scaling of photon energy of free electron lasers.展开更多
Synthesis of multi-color laser pulses has been developed as a promising way to improve low conversion efficiency of high-order harmonic generation(HHG). Here we systematically study the effect of laser focus in a two-...Synthesis of multi-color laser pulses has been developed as a promising way to improve low conversion efficiency of high-order harmonic generation(HHG). Here we systematically study the effect of laser focus in a two-color waveform on generation of macroscopic HHG in soft x-rays. We find that the dependence of HHG yields on laser focus at low or high gas pressure is sensitive to the characteristics of single-atom harmonic response, in which “short”-or “long”-trajectory emissions can be selectively controlled by changing the waveform of two-color synthesized laser pulse. We uncover the phase-matching mechanism of HHG in the gas medium by examining the propagation of the two-color waveform and the evolution of time-frequency emissions of high-harmonic field. We further reveal that the nonlinear effects, such as geometric phase, atomic dispersion, and plasma defocusing, are responsible for modification of two-color waveform upon propagation. This work can be used to find better macroscopic conditions for generating soft x-ray HHG by employing two-color optimized waveforms.展开更多
The Soft X-ray Imager(SXI)is part of the scientific payload of the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission.SMILE is a joint science mission between the European Space Agency(ESA)and the Chinese...The Soft X-ray Imager(SXI)is part of the scientific payload of the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission.SMILE is a joint science mission between the European Space Agency(ESA)and the Chinese Academy of Sciences(CAS)and is due for launch in 2025.SXI is a compact X-ray telescope with a wide field-of-view(FOV)capable of encompassing large portions of Earth’s magnetosphere from the vantage point of the SMILE orbit.SXI is sensitive to the soft X-rays produced by the Solar Wind Charge eXchange(SWCX)process produced when heavy ions of solar wind origin interact with neutral particles in Earth’s exosphere.SWCX provides a mechanism for boundary detection within the magnetosphere,such as the position of Earth’s magnetopause,because the solar wind heavy ions have a very low density in regions of closed magnetic field lines.The sensitivity of the SXI is such that it can potentially track movements of the magnetopause on timescales of a few minutes and the orbit of SMILE will enable such movements to be tracked for segments lasting many hours.SXI is led by the University of Leicester in the United Kingdom(UK)with collaborating organisations on hardware,software and science support within the UK,Europe,China and the United States.展开更多
A study of a nanosecond laser irradiation on the titanium-layer-buried gold planar target is presented. The timeresolved x-ray emission spectra of titanium tracer are measured by a streaked crystal spectrometer. By co...A study of a nanosecond laser irradiation on the titanium-layer-buried gold planar target is presented. The timeresolved x-ray emission spectra of titanium tracer are measured by a streaked crystal spectrometer. By comparing the simulated spectra obtained by using the FLYCHK code with the measured titanium spectra, the temporal plasma states, i.e.,the electron temperatures and densities, are deduced. To evaluate the feasibility of using the method for the characterization of Au plasma states, the deduced plasma states from the measured titanium spectra are compared with the Multi-1D hydrodynamic simulations of laser-produced Au plasmas. By comparing the measured and simulated results, an overall agreement for the electron temperatures is found, whereas there are deviations in the electron densities. The experiment–theory discrepancy may suggest that the plasma state could not be well reproduced by the Multi-1D hydrodynamic simulation, in which the radial gradient is not taken into account. Further investigations on the spectral characterization and hydrodynamic simulations of the plasma states are needed. All the measured and FLYCHK simulated spectra are given in this paper as datasets. The datasets are openly available at http://www.doi.org/10.57760/sciencedb.j00113.00032.展开更多
基金supported by the Czech Academy of Sciences(Mobility Plus Project No.CNRS-23-12)A.M.F.was supported by the Russian Science Foundation(Grant No.20-12-00077).
文摘Coherent motion of particles in a plasma can imprint itself on radiation.The recent advent of high-power lasers—allowing the nonlinear inverse Compton-scattering regime to be reached—has opened the possibility of looking at collective effects in laser–plasma interactions.Under certain conditions,the collective interaction of many electrons with a laser pulse can generate coherent radiation in the hard x-ray regime.This perspective paper explains the limitations under which such a regime might be attained.
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For experiments such as on Ni-like Ag x-ray laser, driven by 1ω laser, the gain region is only several nm depth near the target surface, this paper proposes a new two-layer target, in which a thin layer (several nm depth) of silver is plated on the surface of some other materials. Furthermore, the Ni-like Ag 13.9 nm x-ray laser produced by three new kinds of two-layer target with CH, Al and Ge as foundation, was theoretically studied.
基金suported by the National Natural Science Foundation of China (Grant No. 10874242)the National Basic Research Program of China (973 Program) (Grant No. 2007CB815105)Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20070290008)
文摘Based on the two-dimensional model, this paper compares the hydrodynamics of slab x-ray laser plasma produced by different nonuniform line focused irradiations. It finds that the average intensity and the duration of laser pulse and the overall shape of the intensity distribution in the focal line have different influences on the plasma. Calculations show that the evolution of temperature variation is more sensitive to the pulse duration and the electron density variation is more sensitive to the pulse intensity. Pulses with duration of 200 ps to 500 ps and with intensity of 0.2 TW/cm2 to 1.0 TW/cm2 are proved acceptable in slab x-ray lasers.
基金supported by the National Natural Science Foundation of China ( Grant Nos 60678007,60621063 and 10774184)the State Key Development Program for Basic Research of China (Grant No 2007CB815101)
文摘We investigate the Ne-like Cr x-ray laser at 28.6 nm by using a modified ID lagrangian hydrodynamic code MEDI03 coupled with an atomic physics data package and a 2D ray tracing code as a post-processor. The laser pumping configuration includes two prepulses and one main pulse. The first prepulse normally irradiates the target, while the second prepulse and the main pulse irradiate the target at grazing-incident angles. We predict that saturation can be achieved for the Ne-like Cr x-ray lasers with a total pumping energy of 125mJ, Good beam qualities with no deflecting angle and a small divergence angle of 5 mrad are observed.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10474137,10874242 and 10775018)the National Basic Research Program of China (Grant No 2007CB815105)the Specialized Research Fund for the DoctoralProgram of Higher Education of China (Grant No 20070290008)
文摘A method of studying a non-equilibrium x-ray laser plasma is developed by extending the existing one-dimensional similarity equations to the case of two-dimensional plasma study in the directions perpendicular to the slab and along a focal line. With this method the characteristics of pre-plasma are optimized for transient neon-like Cr x-ray laser. It is found that when the duration and the intensity of 1.053μm pre-pulse are 1.2 ns and 6.5 TW/cm^2 respectively with a delay time of 1.5 ns, the temperature and the temperature discrepancy each approach a proper state, which will provide a uniform distribution of properly ionized neon-like Cr ions before the arrival of pumping pulse.
基金performed under the auspices of the U.S.Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344。
文摘Using an X-ray free electron laser(XFEL)at 960 eV to photo-ionize the 1s electron in neutral neon followed by lasing on the 2p-1s transition in singly-ionized neon,an inner-shell X-ray laser was demonstrated at 849 eV in singly-ionized neon gas several years ago.It took decades to demonstrate this scheme,because it required a very strong X-ray source that could photo-ionize the 1s(K shell)electron in neon on a timescale comparable to the intrinsic Auger lifetime in neon of 2 fs.In this paper,we model the neon inner shell X-ray laser under similar conditions to those used in the XFEL experiments at the SLAC Linac Coherent Light Source(LCLS),and show how we can improve the efficiency of the neon laser and reduce the drive requirements by tuning the XFEL to the 1s-3p transition in neutral neon in order to create gain on the 2p-1s line in neutral neon.We also show how the XFEL could be used to photo-ionize L-shell electrons to drive gain on n=3-2 transitions in singlyionized Ar and Cu plasmas.These bright,coherent,and monochromatic X-ray lasers may prove very useful for doing high-resolution spectroscopy and for studying non-linear process in the X-ray regime.
基金supported by National Natural Science Foundation of China(Nos.11574390,11374360,41472130)the National Basic Research Program of China(No.2013CBA01504)
文摘A simple modified model is presented based on R. A. London's self-similarity model on time-independent ionization hydrodynamics of exploding foil X-ray lasers. In our model, the time-dependent ionization effect is under consideration and the average ion charge depends on the temperature. Then we obtain the new scaling laws for temperature, scale length and electron density, which have better agreement with experimental results.
文摘Gain coefficients are calculated for neon-like gallium and germanium ions. Shorter wavelengths are calculated and predicted to be emitted. The gain coefficients are calculated among 457 energy levels of the neon-like ions. Collisional excitations were calculated through the distorted wave approximations through five electron temperatures T<sub>e</sub> = 300, 500, 700, 1000 and 1500 eV.
基金Supported by the Laser Domain of the Chinese National High Technology Plan。
文摘AmpliHcation of spontaneous emissions at 19.6,23.2 and 23.6 nm have been observed by a “ultiple-Target Series Coupling”design in Ge plasma,.The combined length for four targets is up to 56mm.The gain length product(GL)of small signal is up to 18 for both lines at 23.2 and 23.6 nmt and the effective GL is 16.4 and 15.7 for these two lines respectively.This two lines are obviously tending to saturation.The divergence of x-ray laser beam is about 4 mrad.
基金Supported by the National High Technique 863-410 Project.
文摘An x-ray laser shadowgraphy experiment was conducted on Xingguang-Ⅱ laser facility in 1996.A multi-layer spherical mirror was used as an imaging element and a high sensitivity CCD camera as a detector.We measured the near-field image of the Ti x-ray laser beam.With a Ti x-ray laser beam as a backlight source,we obtained a clear CU mesh image,demonstrating the potential as advanced diagnostic measurements to study high density plasmas in inertial confinement fusion research.
文摘Corrigendum text:There is a misprint in the text of Figs.3 and 4.The text on the bottom part of Figs.3 and 4 should be“100 fs pulse Photoexcitation”and“1 fs pulse Photoexcitation”respectively.This error does not affect any conclusions in this work,and it has been corrected in the printed version of the journal.
基金This work was supported by the Ministry of Science and Technology of the People’s Republic of China(Grant Nos.2018YFA0404803 and 2016YFA0401102)the National Science Foundation of China(Grant No.11935008).
文摘Advances in X-ray laser sources have paved the way to relativistic attosecond X-ray laser pulses and opened up the possibility of exploring highenergy-density physics with this technology.With particle-in-cell simulations,we investigate the interaction of realistic metal crystals with relativistic X-ray laser pulses of parameters that will be available in the near future.A wakefield of the order of TV/cm is excited in the crystal and accelerates trapped electrons stably even though the wakefield is locally modulated by the crystal lattice.Electron injection either occurs at the sharp crystal-vacuum boundary or is controlled by coating the crystal with a high-density film.High-repetition-rate attosecond(20 as)monoenergetic electron beams of energy 125 MeV,charge 100 fC,and emittance 1.6310−9mrad can be produced by shining MHz X-ray laser pulses of energy 2.1 mJ onto coated crystals several micrometers thick.Such a miniature crystal accelerator,which has high reproducibility and allows sufficient control of the parameters of the electron beams,greatly expands the applications of X-ray free electron lasers.For example,it could serve as an ideal electron source for ultrafast electron diffraction and ultrafast electron microscopy to achieve attosecond resolution.
文摘A new type of soft X-ray source, i.e. a plasma-based X-ray laser, is found to be promising to conduct transient measurement. By means of picosecond X-ray laser speckles, the dynamic microscopic polarization clusters within cubic (paraelectric) BaTiO3 was directly observed and characterized in a microscopic scale for the first time. This opens a way to study this type of clusters, which usually manifest large external-field response for ferroelectric materials.
基金National Natural Science Foundation of China(No.11805212)National Key Research and Development Program of China(No.2019YFE03080200)。
文摘Monochromatic x-ray imaging is an essential method for plasma diagnostics related to density information.Large-field high-resolution monochromatic imaging of a He-like iron(Fe XXV)Kαcharacteristic line(6.701 keV)for laser plasma diagnostics was achieved using a developed toroidal crystal x-ray imager.A high-index crystal orientation Ge(531)wafer with a Bragg angle of 75.37°and the toroidal substrate were selected to obtain sufficient diffraction efficiency and compensate for astigmatism under oblique incidence.A precise offline assembly method of the toroidal crystal imager based on energy substitution was proposed,and a spatial resolution of 3-7μm was obtained by toroidal crystal imaging of a 600 line-pairs/inch Au grid within an object field of view larger than 1.0 mm.The toroidal crystal x-ray imager has been successfully tested via side-on backlight imaging experiments of the sinusoidal modulation target and a 1000 line-pairs/inch Au grid with a linewidth of 5μm using an online alignment method based on dual positioning balls to indicate the target and backlighter.This paper describes the optical design,adjustment method,and experimental results of a toroidal crystal system in a laboratory and laser facility.
基金the Fundamental Research Funds for the Central Universities (Grant No. 10822041A2038)。
文摘The generation of hollow atoms will reduce the probability of light absorption and provide a high-quality diffraction image in the experiment. In this paper, we calculated the ionization rate of the Kr atom under x-ray free-electron laser(XFEL) using Hartree–Fock–Slater model and simulated the ionization model of Kr atom using Monte–Carlo method to determine the response of the hollow atom of Kr atom to the XFEL photon energy. Calculating the correlation between the total photoionization cross-section of the ground state of Kr atom and the photon energy, we determined three particular photon energies of 1.75 ke V, 1.90 ke V, and 14.30 ke V. The dynamics simulation under the experimental condition's17.50 ke V photon energy was achieved by implementing the Monte–Carlo method and calibrating the photon flux modeling parameters. Consequently, our calculated data are more consistent with experimental phenomena than previous theoretical studies. The saturable absorption of Kr at 1.75 ke V, 1.90 ke V, 14.30 ke V, and 17.50 ke V energies was further investigated by using the optimized photon flux model theory. We compared the statistics on main ionization paths under those four specific photon energies and calculated the population changes of various Kr hollow atoms with different configurations.The results demonstrate that the population of hollow atoms produced at the critical ionization photon energy is high. Furthermore, the change of population with respect to position is smooth, which shows a significant difference between the generation mode of ions with low and high photon energies. The result is important for the study of medium-and high-Z element hollow atoms, which has substantial implications for the study of hollow atoms with medium and high charge states, as well as for the scaling of photon energy of free electron lasers.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.91950102,12274230,and 11834004)the Funding of Nanjing University of Science and Technology (Grant No.TSXK2022D005)。
文摘Synthesis of multi-color laser pulses has been developed as a promising way to improve low conversion efficiency of high-order harmonic generation(HHG). Here we systematically study the effect of laser focus in a two-color waveform on generation of macroscopic HHG in soft x-rays. We find that the dependence of HHG yields on laser focus at low or high gas pressure is sensitive to the characteristics of single-atom harmonic response, in which “short”-or “long”-trajectory emissions can be selectively controlled by changing the waveform of two-color synthesized laser pulse. We uncover the phase-matching mechanism of HHG in the gas medium by examining the propagation of the two-color waveform and the evolution of time-frequency emissions of high-harmonic field. We further reveal that the nonlinear effects, such as geometric phase, atomic dispersion, and plasma defocusing, are responsible for modification of two-color waveform upon propagation. This work can be used to find better macroscopic conditions for generating soft x-ray HHG by employing two-color optimized waveforms.
基金funding and support from the United Kingdom Space Agency(UKSA)the European Space Agency(ESA)+5 种基金funded and supported through the ESA PRODEX schemefunded through PRODEX PEA 4000123238the Research Council of Norway grant 223252funded by Spanish MCIN/AEI/10.13039/501100011033 grant PID2019-107061GB-C61funding and support from the Chinese Academy of Sciences(CAS)funding and support from the National Aeronautics and Space Administration(NASA)。
文摘The Soft X-ray Imager(SXI)is part of the scientific payload of the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission.SMILE is a joint science mission between the European Space Agency(ESA)and the Chinese Academy of Sciences(CAS)and is due for launch in 2025.SXI is a compact X-ray telescope with a wide field-of-view(FOV)capable of encompassing large portions of Earth’s magnetosphere from the vantage point of the SMILE orbit.SXI is sensitive to the soft X-rays produced by the Solar Wind Charge eXchange(SWCX)process produced when heavy ions of solar wind origin interact with neutral particles in Earth’s exosphere.SWCX provides a mechanism for boundary detection within the magnetosphere,such as the position of Earth’s magnetopause,because the solar wind heavy ions have a very low density in regions of closed magnetic field lines.The sensitivity of the SXI is such that it can potentially track movements of the magnetopause on timescales of a few minutes and the orbit of SMILE will enable such movements to be tracked for segments lasting many hours.SXI is led by the University of Leicester in the United Kingdom(UK)with collaborating organisations on hardware,software and science support within the UK,Europe,China and the United States.
基金Project supported by the National Key Research and Development Program of China (Grant No.2017YFA0403300)the National Natural Science Foundation of China (Grant Nos.12074352 and 11675158)Fundamental Research Funds for the Central Universities in China (Grant No.YJ202144)。
文摘A study of a nanosecond laser irradiation on the titanium-layer-buried gold planar target is presented. The timeresolved x-ray emission spectra of titanium tracer are measured by a streaked crystal spectrometer. By comparing the simulated spectra obtained by using the FLYCHK code with the measured titanium spectra, the temporal plasma states, i.e.,the electron temperatures and densities, are deduced. To evaluate the feasibility of using the method for the characterization of Au plasma states, the deduced plasma states from the measured titanium spectra are compared with the Multi-1D hydrodynamic simulations of laser-produced Au plasmas. By comparing the measured and simulated results, an overall agreement for the electron temperatures is found, whereas there are deviations in the electron densities. The experiment–theory discrepancy may suggest that the plasma state could not be well reproduced by the Multi-1D hydrodynamic simulation, in which the radial gradient is not taken into account. Further investigations on the spectral characterization and hydrodynamic simulations of the plasma states are needed. All the measured and FLYCHK simulated spectra are given in this paper as datasets. The datasets are openly available at http://www.doi.org/10.57760/sciencedb.j00113.00032.