In this study, finite element analysis （FEA） has been used to investigate the effects of different Laval nozzle throat sizes on supersonic molecular beam. The simulations indicate the Mach numbers of the molecular s...In this study, finite element analysis （FEA） has been used to investigate the effects of different Laval nozzle throat sizes on supersonic molecular beam. The simulations indicate the Mach numbers of the molecular stream peak at different positions along the center axis of the beam, which correspond to local minimums of the molecular densities. With the increase of the throat diameter, the first peak of the Mach number increases first and then decreases, while that of the molecular number density increases gradually. Moreover, both first peaks shift progressively away from the throat. At the last part, we discuss the possible applications of our FEA approach to solve some crucial problems met in modern transportations.展开更多
This work studies the angle dependence of the interactions between impinging CH2 particles of 150 eV with the tungsten surface. The simulations show that the carbon atoms are much more easily bonded to the tungsten at...This work studies the angle dependence of the interactions between impinging CH2 particles of 150 eV with the tungsten surface. The simulations show that the carbon atoms are much more easily bonded to the tungsten atoms than hydrogen atoms, though a few of the latter can also penetrate into the tungsten material. When the incidence angle is greater than 75%, the incident CH2 particles are reflected without break-ups. Below this angle, a W-C layer of about 0.5 nm is formed with another C, H-rich layer depositing on top of it. The molecular dynamics （MD） approach has proved to be a powerful tool to solve the structural problems at atomic length scale of various materials. Some of its possible applications to the railway track materials have also been discussed.展开更多
The preparation, characterization, and test of the first wall materials designed to be used in the fusion reactor have remained challenging problems in the material science. This work uses the firstprinciples method a...The preparation, characterization, and test of the first wall materials designed to be used in the fusion reactor have remained challenging problems in the material science. This work uses the firstprinciples method as implemented in the CASTEP package to study the influ ences of the doped titanium carbide on the structural sta bility of the WTiC material. The calculated total energy and enthalpy have been used as criteria to judge the structural models built with consideration of symmetry. Our simulation indicates that the doped TiC tends to form its own domain up to the investigated nanoscale, which implies a possible phase separation. This result reveals the intrinsic reason for the composite nature of the WTiC material and provides an explanation for the experimen tally observed phase separation at the nanoscale. Our approach also sheds a light on explaining the enhancing effects of doped components on the durability, reliability, corrosion resistance, etc., in many special steels.展开更多
The advent of chirped-pulse amplification （CPA） has greatly advanced the field of ultrafast and ultra-intense laser technology. CPA has become an indispensable platform for multidisciplinary research, such as physic...The advent of chirped-pulse amplification （CPA） has greatly advanced the field of ultrafast and ultra-intense laser technology. CPA has become an indispensable platform for multidisciplinary research, such as physics, chemistry, life sciences, and precision metrology. The femtosecond laser facility at the Synergic Extreme Condition User Facility （SECUF） is a comprehensive experimental platform with an advanced femtosecond laser source for ultrafast scientific research. It will provide an ultrafast scientific research system having a few-cycle pulse duration, wide spectral range, high energy, and high repetition rate for multipurpose applications.展开更多
The high harmonic generation(HHG)by few-cycle laser pulses is essential for research in strong-field solid-state physics.Through comparison of high harmonic spectra of solids generated by laser pulses with varying dur...The high harmonic generation(HHG)by few-cycle laser pulses is essential for research in strong-field solid-state physics.Through comparison of high harmonic spectra of solids generated by laser pulses with varying durations,we discovered that lasers with good dispersion compensation are capable of producing a broad spectrum of high harmonics.As the pulse duration is further compressed,several interference peaks appear in the broad spectrum.Moreover,we conducted simulations using the semiconductor Bloch equation,considering the effect of Berry curvature,to better understand this process.Our work provides a valuable approach for studying HHG by few-cycle laser pulses in solid materials,expanding the application of HHG in attosecond physics.展开更多
Isolated attosecond pulse generation in argon is theoretically investigated for different gas pressures and medium lengths.The output of attosecond pulse is effectively enhanced by using a longer gas medium with optim...Isolated attosecond pulse generation in argon is theoretically investigated for different gas pressures and medium lengths.The output of attosecond pulse is effectively enhanced by using a longer gas medium with optimized pressure.The peak intensity of the attosecond pulse by using 6 mm gas medium is doubled compared with that of 1-3 mm gas cell,which is usually used in the experiment.Our simulation shows that the distortion of the driving laser waveform and the absorption are the main factors that limit the output of the attosecond pulse for the long gas medium.Optimized generation condition could be found by balancing the medium length and pressure.展开更多
High harmonic generation(HHG)delivering attosecond pulse duration with photon energy in the extreme ultraviolet spectral range has been demonstrated as a robust table-top coherent light source,allowing for the observa...High harmonic generation(HHG)delivering attosecond pulse duration with photon energy in the extreme ultraviolet spectral range has been demonstrated as a robust table-top coherent light source,allowing for the observation and manipulation of ultrafast process within the shortest time window ever made by humans.The past decade has witnessed the rapid progress of HHG from a variety of solid targets and its application for photoemission spectroscopy in condensed matter.In this article,we review the HHG in solids and the understanding of the underlying physics of HHG,which allows all-optical band structure reconstruction.We also introduce combinations of HHG source and photoemission spectroscopy,such as angular-resolved photoemission spectroscopy and photoemission electron microscopy.With the capacity of exploring a wide momentum space and high temporal resolution,the extension of attosecond science to the field of condensed matter physics will lead to new insights into the fundamental ultrafast dynamics in novel quantum materials.展开更多
基金financially supported by the Science Foundation for International Cooperation of Sichuan Province (2014HH0016)the Fundamental Research Funds for the Central Universities (SWJTU2014: A0920502051113-10000)National Magnetic Confinement Fusion Science Program (2011GB112001)
文摘In this study, finite element analysis （FEA） has been used to investigate the effects of different Laval nozzle throat sizes on supersonic molecular beam. The simulations indicate the Mach numbers of the molecular stream peak at different positions along the center axis of the beam, which correspond to local minimums of the molecular densities. With the increase of the throat diameter, the first peak of the Mach number increases first and then decreases, while that of the molecular number density increases gradually. Moreover, both first peaks shift progressively away from the throat. At the last part, we discuss the possible applications of our FEA approach to solve some crucial problems met in modern transportations.
基金financially supported by the Science Foundation for International Cooperation of Sichuan Province (2014HH0016)the Fundamental Research Funds for the Central Universities (SWJTU2014: A0920502051113-10000)National Magnetic Confinement Fusion Science Program (2011GB112001)
文摘This work studies the angle dependence of the interactions between impinging CH2 particles of 150 eV with the tungsten surface. The simulations show that the carbon atoms are much more easily bonded to the tungsten atoms than hydrogen atoms, though a few of the latter can also penetrate into the tungsten material. When the incidence angle is greater than 75%, the incident CH2 particles are reflected without break-ups. Below this angle, a W-C layer of about 0.5 nm is formed with another C, H-rich layer depositing on top of it. The molecular dynamics （MD） approach has proved to be a powerful tool to solve the structural problems at atomic length scale of various materials. Some of its possible applications to the railway track materials have also been discussed.
基金finantially supported by the Science Foundation for International Cooperation of Sichuan Province (2014HH0016)the Fundamental Research Funds for the Central Universities (SWJTU2014: A0920502051113-10000)National Magnetic Confinement Fusion Science Program (2011GB112001)
文摘The preparation, characterization, and test of the first wall materials designed to be used in the fusion reactor have remained challenging problems in the material science. This work uses the firstprinciples method as implemented in the CASTEP package to study the influ ences of the doped titanium carbide on the structural sta bility of the WTiC material. The calculated total energy and enthalpy have been used as criteria to judge the structural models built with consideration of symmetry. Our simulation indicates that the doped TiC tends to form its own domain up to the investigated nanoscale, which implies a possible phase separation. This result reveals the intrinsic reason for the composite nature of the WTiC material and provides an explanation for the experimen tally observed phase separation at the nanoscale. Our approach also sheds a light on explaining the enhancing effects of doped components on the durability, reliability, corrosion resistance, etc., in many special steels.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61575217 and 11774410)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB16030200)
文摘The advent of chirped-pulse amplification （CPA） has greatly advanced the field of ultrafast and ultra-intense laser technology. CPA has become an indispensable platform for multidisciplinary research, such as physics, chemistry, life sciences, and precision metrology. The femtosecond laser facility at the Synergic Extreme Condition User Facility （SECUF） is a comprehensive experimental platform with an advanced femtosecond laser source for ultrafast scientific research. It will provide an ultrafast scientific research system having a few-cycle pulse duration, wide spectral range, high energy, and high repetition rate for multipurpose applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91850209 and 11974416)。
文摘The high harmonic generation(HHG)by few-cycle laser pulses is essential for research in strong-field solid-state physics.Through comparison of high harmonic spectra of solids generated by laser pulses with varying durations,we discovered that lasers with good dispersion compensation are capable of producing a broad spectrum of high harmonics.As the pulse duration is further compressed,several interference peaks appear in the broad spectrum.Moreover,we conducted simulations using the semiconductor Bloch equation,considering the effect of Berry curvature,to better understand this process.Our work provides a valuable approach for studying HHG by few-cycle laser pulses in solid materials,expanding the application of HHG in attosecond physics.
基金Project supported by the National Key R&D Program of China(Grant No.2018YFB1107200)the National Natural Science Foundation of China(Grant Nos.11974416 and 91850209)。
文摘Isolated attosecond pulse generation in argon is theoretically investigated for different gas pressures and medium lengths.The output of attosecond pulse is effectively enhanced by using a longer gas medium with optimized pressure.The peak intensity of the attosecond pulse by using 6 mm gas medium is doubled compared with that of 1-3 mm gas cell,which is usually used in the experiment.Our simulation shows that the distortion of the driving laser waveform and the absorption are the main factors that limit the output of the attosecond pulse for the long gas medium.Optimized generation condition could be found by balancing the medium length and pressure.
基金supported by the National Natural Science Foundation of China(Grant Nos.91850209,12174435 and 12034020)the National Key Research and Development Program of China(2017YFB0405202,2018YFB1107200).
文摘High harmonic generation(HHG)delivering attosecond pulse duration with photon energy in the extreme ultraviolet spectral range has been demonstrated as a robust table-top coherent light source,allowing for the observation and manipulation of ultrafast process within the shortest time window ever made by humans.The past decade has witnessed the rapid progress of HHG from a variety of solid targets and its application for photoemission spectroscopy in condensed matter.In this article,we review the HHG in solids and the understanding of the underlying physics of HHG,which allows all-optical band structure reconstruction.We also introduce combinations of HHG source and photoemission spectroscopy,such as angular-resolved photoemission spectroscopy and photoemission electron microscopy.With the capacity of exploring a wide momentum space and high temporal resolution,the extension of attosecond science to the field of condensed matter physics will lead to new insights into the fundamental ultrafast dynamics in novel quantum materials.
