We demonstrate a new polarization smoothing(PS)approach utilizing residual stress birefringence in fused silica to create a spatially random polarization control plate(SRPCP),thereby improving target illumination unif...We demonstrate a new polarization smoothing(PS)approach utilizing residual stress birefringence in fused silica to create a spatially random polarization control plate(SRPCP),thereby improving target illumination uniformity in inertial confinement fusion(ICF)laser systems.The fundamental operating mechanism and key fabrication techniques for the SRPCP are systematically developed and experimentally validated.The SRPCP converts a linearly polarized 3ω incident laser beam into an output beam with a spatially randomized polarization distribution.When combined with a continuous phase plate,the SRPCP effectively suppresses high-intensity speckles at all spatial frequencies in the focal spot.The proposed PS technique is specifically designed for high-fluence large-aperture laser systems,enabling novel polarization control regimes in laser-driven ICF.展开更多
In the design and construction of ultra-high-peak-power laser systems,it is necessary to control the accumulated B-integral of the laser pulse,but currently there are no reasonable B-integral control standards for pic...In the design and construction of ultra-high-peak-power laser systems,it is necessary to control the accumulated B-integral of the laser pulse,but currently there are no reasonable B-integral control standards for picosecond and femtosecond lasers.We systematically evaluate the influence of the B-integral on the output capability of picosecond and femtosecond laser systems for the first time,to our knowledge,taking Nd:glass lasers and Ti:sapphire lasers as examples.For picosecond lasers,the temporal domain compressibility and the small-scale self-focusing effect restrict the B-integral to 1.7 and 1.9,respectively.For femtosecond lasers,the B-integral is mainly restricted by the small-scale self-focusing effect and the far-field focusability,which limit the B-integral to 1.5 and 1.7,respectively.The restriction made by far-field focusability can be largely relaxed by inserting a deformable mirror.The study of the factors restricting the B-integral will provide guidance for the design of ultra-high-peak-power laser systems.展开更多
We present experimental results on kilojoule ultraviolet laser output with 1%spectral broadening.Through stimulated rotational Raman scattering(SRRS)with signal laser injection,we achieve effective spectral broadening...We present experimental results on kilojoule ultraviolet laser output with 1%spectral broadening.Through stimulated rotational Raman scattering(SRRS)with signal laser injection,we achieve effective spectral broadening in short-range propagation,with good retention of the original near-field distribution and time waveform.Theoretical calculations show that 2%bandwidth spectral broadening can be achieved by injecting 20 kW/cm^(2) signal light at 2.2 GW/cm^(2) flux of the pump laser.In addition,high-frequency modulation in the near field can be effectively avoided through replacement of the original random noise signal light by the controllable signal light.The SRRS in the atmospheric environment excited with signal laser injection can provide wide-band light output with controllable beam quality without long-distance propagation,representing an important potential route to realization of broadband laser drivers.展开更多
Zirconium alloys are critical materials in nuclear engineering due to their exceptional irradiation resistance and corrosion stability.However,prolonged exposure to extreme operational environments,including a high ra...Zirconium alloys are critical materials in nuclear engineering due to their exceptional irradiation resistance and corrosion stability.However,prolonged exposure to extreme operational environments,including a high radiation,mechanical stress,and corrosive media,induces surface degradation mechanisms including stress corrosion cracking and erosion from impurity particle impacts,necessitating advanced surface treatments to improve hardness and corrosion resistance.We explore the application of laser shock peening(LSP)to enhance the surface properties of the Zr4 alloy.Experimental analyses reveal substantial microstructural modifications upon the LSP.The surface grain refinement achieved a maximum reduction of 52.7%in average grain size(from 22.88 to 10.8μm^(2)),accompanied by an increase of 59%in hardness(204 to 326 HV).Additionally,a compressive residual stress layer(approximately-100 MPa)was generated on the treated surface,which reduces the risk of stress corrosion cracking.To elucidate the mechanistic basis of these improvements,a multiscale computational framework was developed,integrating finite-element models for macroscale stress field evolution and molecular dynamics simulations for nanoscale dislocation dynamics.By incorporating the strain rate as a critical variable,this framework bridges microstructure evolution with macroscopic mechanical enhancements.The simulations not only elucidated the dynamic interplay between shockwave-induced plastic deformation and property improvements but also exhibited a good consistency with experimental residual stress profiles.Notably,we propose the application of strain rate-driven multiscale modeling in LSP research for Zr alloys,providing a predictive method to optimize laser parameters for a tailored surface strengthening.This study not only confirms that LSP is a feasible strategy capable of effectively enhancing the comprehensive surface properties of Zr alloys and extending their service life in nuclear environments,but also provides a reliable simulation methodology in the field of laser surface engineering of alloy materials.展开更多
A reshock experiment for investigating the growth of material mixing driven by the Richtmyer–Meshkov instability has been conducted at the SG 100 kJ Laser Facility.We present a novel measurement technique for capturi...A reshock experiment for investigating the growth of material mixing driven by the Richtmyer–Meshkov instability has been conducted at the SG 100 kJ Laser Facility.We present a novel measurement technique for capturing the density field and the temporal evolution of the mixing width in rough aluminum subjected to reshocks under extreme conditions.The temporal evolution of the aluminum layer width obtained from backlit X-ray radiography demonstrates a sharp increase in width caused by reshocks,and simulations using the BHR-2 turbulent mixing model show excellent agreement with the measured aluminum layer width.Moreover,by utilizing a quasi-monochromatic X-ray imaging system at 5.2 keV,based on Bragg reflection from a spherically curved quartz crystal,we demonstrate direct quantification of the aluminum density field in mixed regions for the first time in a indirectly driven reshock experiment.The deviation between the calculated and actual density values is significantly less than 10%when the density of the aluminum region is below 0.7 g/cm3.The density field provides further information about variable-density turbulent mixing,which improves the constraints on simulations and enhances predictive capabilities for inertial confinement fusion target design and astrophysical shock scenarios.展开更多
Stimulated Raman scattering(SRS)under a new ignition path that combines the advantages of direct-drive(DD)and indirect-drive(ID)schemes is investigated experimentally at the Shenguang-100 kJ facility.The results show ...Stimulated Raman scattering(SRS)under a new ignition path that combines the advantages of direct-drive(DD)and indirect-drive(ID)schemes is investigated experimentally at the Shenguang-100 kJ facility.The results show that collective SRS in the plasma produced by ablating a polyimide film is detected for the ID beams,but is suppressed by adding a toe before the main pulse of the ID beams.The toe also strongly influences SRS of both the ID and DD beams excited in the plasma generated in the hohlraum.When a toe is used,the SRS spectra of the DD beams show that SRS tends to be excited in lower plasma density,which will result in a lower risk of super-hot electrons.Measurements of hot electrons support this conclusion.This research will help us produce a better pulse design for this new ignition path.展开更多
High-power laser pulses interacting with targets can generate intense electromagnetic pulses(EMPs),which can disrupt physical experimental diagnostics and even damage diagnostic equipment,posing a threat to the reliab...High-power laser pulses interacting with targets can generate intense electromagnetic pulses(EMPs),which can disrupt physical experimental diagnostics and even damage diagnostic equipment,posing a threat to the reliable operation of experiments.In this study,EMPs resulting from multi-petawatt laser irradiating nitrogen gas jets were systematically analyzed and investigated.The experimental results revealed that the EMP amplitude is positively correlated with the quantity and energy of the electrons captured and accelerated by the plasma channel.These factors are reflected by parameters such as laser energy and nitrogen gas jet pressure.Additionally,we propose several potential sources of EMPs produced by laser-irradiated gas jets and separately analyzed their spatiotemporal distributions.The findings provide insight into the mechanisms of EMP generation and introduce a new approach to achieve controllable EMPs by regulating the laser energy and gas jet pressure.展开更多
Shock compression driven by nanosecond-laser techniques generates extreme pressure and temperature conditions in materials,enabling the study of high-pressure phase transitions and the behavior of materials in extreme...Shock compression driven by nanosecond-laser techniques generates extreme pressure and temperature conditions in materials,enabling the study of high-pressure phase transitions and the behavior of materials in extreme environments.These dynamic high-pressure states are relevant to a wide range of phenomena,including planetary formation,asteroid impacts,spacecraft shielding,and inertial confinement fusion.The integration of advanced X-ray diffraction experimental techniques,from laser-induced X-ray sources and X-ray free-electron lasers,and theoretical simulations has provided unprecedented insights into material behavior under extreme conditions.This perspective reviews recent advances in dynamic high-pressure research and the insights that they can provide,concentrating on dynamical phase transitions,metastable and transient states,the influence of crystal orientation,microstructural changes,and the kinetic mechanism of phase transitions across a variety of interdisciplinary fields.展开更多
Correction to:Nuclear Science and Techniques(2025)36:100 https://doi.org/10.1007/s41365-025-01692-6 In this article,Fig.9 appeared incorrectly and have now been corrected in the original publication.For completeness a...Correction to:Nuclear Science and Techniques(2025)36:100 https://doi.org/10.1007/s41365-025-01692-6 In this article,Fig.9 appeared incorrectly and have now been corrected in the original publication.For completeness and transparency,both correct and incorrect versions are displayed below.展开更多
Here we report a femtosecond laser direct writing(a precise 3D printing also known as two-photon polymerization lithography) of hybrid organic-inorganic SZ2080^(TM)pre-polymer without using any photo-initiator and app...Here we report a femtosecond laser direct writing(a precise 3D printing also known as two-photon polymerization lithography) of hybrid organic-inorganic SZ2080^(TM)pre-polymer without using any photo-initiator and applying ~100 fs oscillator operating at 517 nm wavelength and 76 MHz repetition rate. The proof of concept was experimentally demonstrated and benchmarking 3D woodpile nanostructures, micro-scaffolds, free-form micro-object “Benchy” and bulk micro-cubes are successfully produced. The essential novelty underlies the fact that non-amplified laser systems delivering just 40-500 p J individual pulses are sufficient for inducing localized cross-linking reactions within hundreds of nanometers in cross sections. And it is opposed to the prejudice that higher pulse energies and lower repetition rates of amplified lasers are necessary for structuring non-photosensitized polymers. The experimental work is of high importance for fundamental understanding of laser enabled nanoscale 3D additive manufacturing and widens technology’ s field of applications where the avoidance of photo-initiator is preferable or is even a necessity, such as micro-optics, nano-photonics, and biomedicine.展开更多
We have carried out the hohlraum experiments about radiation temperature scaling on the Shenguang-Ⅱ （SG- Ⅱ） laser facility with eight laser beams of 0.35#m, pulse duration of about 1.0ns and total energy of 2000J....We have carried out the hohlraum experiments about radiation temperature scaling on the Shenguang-Ⅱ （SG- Ⅱ） laser facility with eight laser beams of 0.35#m, pulse duration of about 1.0ns and total energy of 2000J. The reradiated x-ray flux through the laser entrance hole was measured using a soft x-ray spectrometer. The measured peak radiation temperature was 170eV for the standard hohlraum and 150 eV for the 1.5-scaled one. We have derived the radiation temperature scaling law, in which the laser hohlraum coupling efficiency is included. With an appropriate coupling efficiency, the coincidences between experimental and scaling hohlraum radiation temperatures are rather good.展开更多
By employing three reflecting volume Bragg gratings, a near-infrared 4-channel spectral-beam-combining system is demonstrated to present 720 W combined power with a combining efficiency of 94.7%. The combined laser be...By employing three reflecting volume Bragg gratings, a near-infrared 4-channel spectral-beam-combining system is demonstrated to present 720 W combined power with a combining efficiency of 94.7%. The combined laser beam is near-diffraction-limited with a beam factor M^2-1.54. During this 4-channel beam-combining process, no special active cooling measures are used to evaluate the volume Bragg gratings as combining elements are under the higher power laser operation. Thermal expansion and period distortion are verified in a 2 k W 2-channel beam-combining process, and the heat issue in the transmission case is found to be more remarkable than that in the diffraction e-se. Transmitted and diffracted beams experience wave-front aberrations with different degrees, thus leading to distinct beam deterioration.展开更多
The SG-Ⅲlaser facility(SG-Ⅲ)is the largest laser driver for inertial confinement fusion(ICF)researches in China,which has 48 beamlines and can deliver 180 kJ ultraviolet laser energy in 3 ns.In order to meet the req...The SG-Ⅲlaser facility(SG-Ⅲ)is the largest laser driver for inertial confinement fusion(ICF)researches in China,which has 48 beamlines and can deliver 180 kJ ultraviolet laser energy in 3 ns.In order to meet the requirements of precise physics experiments,some new functionalities need to be added to SG-Ⅲand some intrinsic laser performances need upgrade.So at the end of SG-Ⅲ's engineering construction,the 2-year laser performance upgrade project started.This paper will introduce the newly added functionalities and the latest laser performance of SG-Ⅲ.With these function extensions and performance upgrade,SG-Ⅲis now fully prepared for precise ICF experiments and solidly paves the way towards fusion ignition.展开更多
A 4 kW fiber laser was chosen to weld the new hot-rolled nano-scale precipitation-strengthened steel with a thickness of 4.5 mm. The effect of laser power, defocusing distance, and welding speed on the welded joint ap...A 4 kW fiber laser was chosen to weld the new hot-rolled nano-scale precipitation-strengthened steel with a thickness of 4.5 mm. The effect of laser power, defocusing distance, and welding speed on the welded joint appearance was examined, and the microstructure and mechanical properties on the typical butt joints were investigated. Results showed that increasing laser welding power may cause faster downward flow of molten metal to produce greater root humping. With the welding speed increasing, the average welding seam （WS） width decreased, and the average WS and heat-affected zone （HAZ） hardness increased. The microstructures of WS, fusion line, and coarse grain heat-affected zone were lath martensite, but the growth direction of the original austenite grain boundaries was significantly different. The microstructures of fine grain heat-affected zone were ferrite and martensite, and the microstructure of mixed grain heat- affected zone contained ferrite, massive M/A island, and a small amount of martensite. The micro-hardness values of WS, HAZ, and base metal （BM） were 358, 302, and 265 HV, respectively. The butt joint fracture at the BM far from the WS and the welded joint tensile strength are observed to follow proportional relationship with hardness.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.62275235).
文摘We demonstrate a new polarization smoothing(PS)approach utilizing residual stress birefringence in fused silica to create a spatially random polarization control plate(SRPCP),thereby improving target illumination uniformity in inertial confinement fusion(ICF)laser systems.The fundamental operating mechanism and key fabrication techniques for the SRPCP are systematically developed and experimentally validated.The SRPCP converts a linearly polarized 3ω incident laser beam into an output beam with a spatially randomized polarization distribution.When combined with a continuous phase plate,the SRPCP effectively suppresses high-intensity speckles at all spatial frequencies in the focal spot.The proposed PS technique is specifically designed for high-fluence large-aperture laser systems,enabling novel polarization control regimes in laser-driven ICF.
基金supported by the National Key Laboratory of Plasma Physics Fund(Nos.6142A04220204 and6142A04230303)the Independent Research Project of the National Key Laboratory of Plasma Physics(Nos.JCKYS2023212802 and JCKYS2024212806)the National Key Research and Development Program of China(No.2022YFB3606305)。
文摘In the design and construction of ultra-high-peak-power laser systems,it is necessary to control the accumulated B-integral of the laser pulse,but currently there are no reasonable B-integral control standards for picosecond and femtosecond lasers.We systematically evaluate the influence of the B-integral on the output capability of picosecond and femtosecond laser systems for the first time,to our knowledge,taking Nd:glass lasers and Ti:sapphire lasers as examples.For picosecond lasers,the temporal domain compressibility and the small-scale self-focusing effect restrict the B-integral to 1.7 and 1.9,respectively.For femtosecond lasers,the B-integral is mainly restricted by the small-scale self-focusing effect and the far-field focusability,which limit the B-integral to 1.5 and 1.7,respectively.The restriction made by far-field focusability can be largely relaxed by inserting a deformable mirror.The study of the factors restricting the B-integral will provide guidance for the design of ultra-high-peak-power laser systems.
基金supported by the Presidential Foundation of CAEP(Grant No.YZJJZL2023116)the National Nature Science Foundation of China(Grant No.12275249)the Youth Talent Fund of the Laser Fusion Research Center,CAEP(Grant Nos.RCFCZ7-2024-2 and RCFPD4-2020-4).
文摘We present experimental results on kilojoule ultraviolet laser output with 1%spectral broadening.Through stimulated rotational Raman scattering(SRRS)with signal laser injection,we achieve effective spectral broadening in short-range propagation,with good retention of the original near-field distribution and time waveform.Theoretical calculations show that 2%bandwidth spectral broadening can be achieved by injecting 20 kW/cm^(2) signal light at 2.2 GW/cm^(2) flux of the pump laser.In addition,high-frequency modulation in the near field can be effectively avoided through replacement of the original random noise signal light by the controllable signal light.The SRRS in the atmospheric environment excited with signal laser injection can provide wide-band light output with controllable beam quality without long-distance propagation,representing an important potential route to realization of broadband laser drivers.
基金Supported by National Key Research and Development Program of China(Grant No.2023YFB4603803)National Natural Science Foundation of China(Grant No.12374295).
文摘Zirconium alloys are critical materials in nuclear engineering due to their exceptional irradiation resistance and corrosion stability.However,prolonged exposure to extreme operational environments,including a high radiation,mechanical stress,and corrosive media,induces surface degradation mechanisms including stress corrosion cracking and erosion from impurity particle impacts,necessitating advanced surface treatments to improve hardness and corrosion resistance.We explore the application of laser shock peening(LSP)to enhance the surface properties of the Zr4 alloy.Experimental analyses reveal substantial microstructural modifications upon the LSP.The surface grain refinement achieved a maximum reduction of 52.7%in average grain size(from 22.88 to 10.8μm^(2)),accompanied by an increase of 59%in hardness(204 to 326 HV).Additionally,a compressive residual stress layer(approximately-100 MPa)was generated on the treated surface,which reduces the risk of stress corrosion cracking.To elucidate the mechanistic basis of these improvements,a multiscale computational framework was developed,integrating finite-element models for macroscale stress field evolution and molecular dynamics simulations for nanoscale dislocation dynamics.By incorporating the strain rate as a critical variable,this framework bridges microstructure evolution with macroscopic mechanical enhancements.The simulations not only elucidated the dynamic interplay between shockwave-induced plastic deformation and property improvements but also exhibited a good consistency with experimental residual stress profiles.Notably,we propose the application of strain rate-driven multiscale modeling in LSP research for Zr alloys,providing a predictive method to optimize laser parameters for a tailored surface strengthening.This study not only confirms that LSP is a feasible strategy capable of effectively enhancing the comprehensive surface properties of Zr alloys and extending their service life in nuclear environments,but also provides a reliable simulation methodology in the field of laser surface engineering of alloy materials.
基金supported by the National Key R&D Program of China(Grant No.2023YFA1608400)the National Natural Science Foundation of China(Grant Nos.12205275 and 12588301).
文摘A reshock experiment for investigating the growth of material mixing driven by the Richtmyer–Meshkov instability has been conducted at the SG 100 kJ Laser Facility.We present a novel measurement technique for capturing the density field and the temporal evolution of the mixing width in rough aluminum subjected to reshocks under extreme conditions.The temporal evolution of the aluminum layer width obtained from backlit X-ray radiography demonstrates a sharp increase in width caused by reshocks,and simulations using the BHR-2 turbulent mixing model show excellent agreement with the measured aluminum layer width.Moreover,by utilizing a quasi-monochromatic X-ray imaging system at 5.2 keV,based on Bragg reflection from a spherically curved quartz crystal,we demonstrate direct quantification of the aluminum density field in mixed regions for the first time in a indirectly driven reshock experiment.The deviation between the calculated and actual density values is significantly less than 10%when the density of the aluminum region is below 0.7 g/cm3.The density field provides further information about variable-density turbulent mixing,which improves the constraints on simulations and enhances predictive capabilities for inertial confinement fusion target design and astrophysical shock scenarios.
基金supported by the National Natural Science Foundation of China(Grant Nos.12205274,12275251,12105270,12205272,12305262,and 12035002)the National Key Laboratory of Plasma Physics(Grant No.JCKYS2024212803)+2 种基金the Fund of the National Key Laboratory of Plasma Physics(Grant No.6142A04230103)the National Key R&D Program of China(Grant No.2023YFA1608400)the National Security Academic Fund(Grant No.U2430207).
文摘Stimulated Raman scattering(SRS)under a new ignition path that combines the advantages of direct-drive(DD)and indirect-drive(ID)schemes is investigated experimentally at the Shenguang-100 kJ facility.The results show that collective SRS in the plasma produced by ablating a polyimide film is detected for the ID beams,but is suppressed by adding a toe before the main pulse of the ID beams.The toe also strongly influences SRS of both the ID and DD beams excited in the plasma generated in the hohlraum.When a toe is used,the SRS spectra of the DD beams show that SRS tends to be excited in lower plasma density,which will result in a lower risk of super-hot electrons.Measurements of hot electrons support this conclusion.This research will help us produce a better pulse design for this new ignition path.
基金supported by the National Grand Instrument Project(No.2019YFF01014404)the Natural Science Foundation of China(Nos.12122501,61631001,11921006,U2241281,and 11975037)the Foundation of Science and Technology on Plasma Physics Laboratory(No.6142A04220108)。
文摘High-power laser pulses interacting with targets can generate intense electromagnetic pulses(EMPs),which can disrupt physical experimental diagnostics and even damage diagnostic equipment,posing a threat to the reliable operation of experiments.In this study,EMPs resulting from multi-petawatt laser irradiating nitrogen gas jets were systematically analyzed and investigated.The experimental results revealed that the EMP amplitude is positively correlated with the quantity and energy of the electrons captured and accelerated by the plasma channel.These factors are reflected by parameters such as laser energy and nitrogen gas jet pressure.Additionally,we propose several potential sources of EMPs produced by laser-irradiated gas jets and separately analyzed their spatiotemporal distributions.The findings provide insight into the mechanisms of EMP generation and introduce a new approach to achieve controllable EMPs by regulating the laser energy and gas jet pressure.
基金supported by the National Natural Science Foundation of China under Grant Nos.12534013,12035002,12047561,and 12104507as well as the Science and Technology Innovation Program of Hunan Province under Grant No.2021RC4026+1 种基金T.Sekine gratefully acknowledges financial support from the Shanghai Key Laboratory of Material Frontiers Research in Extreme Environments,China(Grant No.22dz2260800)from the Shanghai Science and Technology Committee,China(Grant No.22JC1410300).
文摘Shock compression driven by nanosecond-laser techniques generates extreme pressure and temperature conditions in materials,enabling the study of high-pressure phase transitions and the behavior of materials in extreme environments.These dynamic high-pressure states are relevant to a wide range of phenomena,including planetary formation,asteroid impacts,spacecraft shielding,and inertial confinement fusion.The integration of advanced X-ray diffraction experimental techniques,from laser-induced X-ray sources and X-ray free-electron lasers,and theoretical simulations has provided unprecedented insights into material behavior under extreme conditions.This perspective reviews recent advances in dynamic high-pressure research and the insights that they can provide,concentrating on dynamical phase transitions,metastable and transient states,the influence of crystal orientation,microstructural changes,and the kinetic mechanism of phase transitions across a variety of interdisciplinary fields.
文摘Correction to:Nuclear Science and Techniques(2025)36:100 https://doi.org/10.1007/s41365-025-01692-6 In this article,Fig.9 appeared incorrectly and have now been corrected in the original publication.For completeness and transparency,both correct and incorrect versions are displayed below.
基金Project(S-MIP-20-17) supported by the Research Council of LithuaniaProject(871124) supported by the EU Horizon 2020, Research and Innovation program LASERLAB-EUROPE JRA。
文摘Here we report a femtosecond laser direct writing(a precise 3D printing also known as two-photon polymerization lithography) of hybrid organic-inorganic SZ2080^(TM)pre-polymer without using any photo-initiator and applying ~100 fs oscillator operating at 517 nm wavelength and 76 MHz repetition rate. The proof of concept was experimentally demonstrated and benchmarking 3D woodpile nanostructures, micro-scaffolds, free-form micro-object “Benchy” and bulk micro-cubes are successfully produced. The essential novelty underlies the fact that non-amplified laser systems delivering just 40-500 p J individual pulses are sufficient for inducing localized cross-linking reactions within hundreds of nanometers in cross sections. And it is opposed to the prejudice that higher pulse energies and lower repetition rates of amplified lasers are necessary for structuring non-photosensitized polymers. The experimental work is of high importance for fundamental understanding of laser enabled nanoscale 3D additive manufacturing and widens technology’ s field of applications where the avoidance of photo-initiator is preferable or is even a necessity, such as micro-optics, nano-photonics, and biomedicine.
文摘We have carried out the hohlraum experiments about radiation temperature scaling on the Shenguang-Ⅱ （SG- Ⅱ） laser facility with eight laser beams of 0.35#m, pulse duration of about 1.0ns and total energy of 2000J. The reradiated x-ray flux through the laser entrance hole was measured using a soft x-ray spectrometer. The measured peak radiation temperature was 170eV for the standard hohlraum and 150 eV for the 1.5-scaled one. We have derived the radiation temperature scaling law, in which the laser hohlraum coupling efficiency is included. With an appropriate coupling efficiency, the coincidences between experimental and scaling hohlraum radiation temperatures are rather good.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11474257 and 61605183
文摘By employing three reflecting volume Bragg gratings, a near-infrared 4-channel spectral-beam-combining system is demonstrated to present 720 W combined power with a combining efficiency of 94.7%. The combined laser beam is near-diffraction-limited with a beam factor M^2-1.54. During this 4-channel beam-combining process, no special active cooling measures are used to evaluate the volume Bragg gratings as combining elements are under the higher power laser operation. Thermal expansion and period distortion are verified in a 2 k W 2-channel beam-combining process, and the heat issue in the transmission case is found to be more remarkable than that in the diffraction e-se. Transmitted and diffracted beams experience wave-front aberrations with different degrees, thus leading to distinct beam deterioration.
基金This work is supported by the SG-Ⅲ performance upgrade project.
文摘The SG-Ⅲlaser facility(SG-Ⅲ)is the largest laser driver for inertial confinement fusion(ICF)researches in China,which has 48 beamlines and can deliver 180 kJ ultraviolet laser energy in 3 ns.In order to meet the requirements of precise physics experiments,some new functionalities need to be added to SG-Ⅲand some intrinsic laser performances need upgrade.So at the end of SG-Ⅲ's engineering construction,the 2-year laser performance upgrade project started.This paper will introduce the newly added functionalities and the latest laser performance of SG-Ⅲ.With these function extensions and performance upgrade,SG-Ⅲis now fully prepared for precise ICF experiments and solidly paves the way towards fusion ignition.
基金supported by the National Natural Science Foundation of China (Nos.51305285 and 51104110)the Basic Research Program of Jiangsu Province (Nos. BK20130315 and BK20130304)
文摘A 4 kW fiber laser was chosen to weld the new hot-rolled nano-scale precipitation-strengthened steel with a thickness of 4.5 mm. The effect of laser power, defocusing distance, and welding speed on the welded joint appearance was examined, and the microstructure and mechanical properties on the typical butt joints were investigated. Results showed that increasing laser welding power may cause faster downward flow of molten metal to produce greater root humping. With the welding speed increasing, the average welding seam （WS） width decreased, and the average WS and heat-affected zone （HAZ） hardness increased. The microstructures of WS, fusion line, and coarse grain heat-affected zone were lath martensite, but the growth direction of the original austenite grain boundaries was significantly different. The microstructures of fine grain heat-affected zone were ferrite and martensite, and the microstructure of mixed grain heat- affected zone contained ferrite, massive M/A island, and a small amount of martensite. The micro-hardness values of WS, HAZ, and base metal （BM） were 358, 302, and 265 HV, respectively. The butt joint fracture at the BM far from the WS and the welded joint tensile strength are observed to follow proportional relationship with hardness.
