The third paragraph in Sec.IV REGENERATIVE AMPLIFICATION erroneously states“In other words,the distribution of spectral components is time-dependent,and the spectral distortion in the amplification process will not c...The third paragraph in Sec.IV REGENERATIVE AMPLIFICATION erroneously states“In other words,the distribution of spectral components is time-dependent,and the spectral distortion in the amplification process will not change the time-domain shape.”展开更多
Broadband low-coherence light is considered to be an effective way to suppress laser plasma instability.Recent studies have demonstrated the ability of low-coherence laser facilities to reduce back-scattering during b...Broadband low-coherence light is considered to be an effective way to suppress laser plasma instability.Recent studies have demonstrated the ability of low-coherence laser facilities to reduce back-scattering during beam–target coupling.However,to ensure simultaneous low coherence and high energy,complex spectral modulation methods and amplification routes have to be adopted.In this work,we propose the use of a random fiber laser(RFL)as the seed source.The spectral features of this RFL can be carefully tailored to provide a good match with the gain characteristics of the laser amplification medium,thus enabling efficient amplification while maintaining low coherence.First,a theoretical model is constructed to give a comprehensive description of the output characteristics of the spectrum-tailored RFL,after which the designed RFL is experimentally realized as a seed source.Through precise pulse shaping and efficient regenerative amplification,a shaped random laser pulse output of 28 mJ is obtained,which is the first random laser system with megawatt-class peak power that is able to achieve low coherence and efficient spectrum-conformal regenerative amplification.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
In this paper,we give a review of our theoretical and experimental progress in octahedral spherical hohlraum study.From our theoretical study,the octahedral spherical hohlraums with 6 Laser Entrance Holes(LEHs)of octa...In this paper,we give a review of our theoretical and experimental progress in octahedral spherical hohlraum study.From our theoretical study,the octahedral spherical hohlraums with 6 Laser Entrance Holes(LEHs)of octahedral symmetry have robust high symmetry during the capsule implosion at hohlraum-to-capsule radius ratio larger than 3.7.In addition,the octahedral spherical hohlraums also have potential superiority on low backscattering without supplementary technology.We studied the laser arrangement and constraints of the octahedral spherical hohlraums,and gave a design on the laser arrangement for ignition octahedral hohlraums.As a result,the injection angle of laser beams of 50°-60°was proposed as the optimum candidate range for the octahedral spherical hohlraums.We proposed a novel octahedral spherical hohlraum with cylindrical LEHs and LEH shields,in order to increase the laser coupling efficiency and improve the capsule symmetry and to mitigate the influence of the wall blowoff on laser transport.We studied on the sensitivity of the octahedral spherical hohlraums to random errors and compared the sensitivity among the octahedral spherical hohlraums,the rugby hohlraums and the cylindrical hohlraums,and the results show that the octahedral spherical hohlraums are robust to these random errors while the cylindrical hohlraums are the most sensitive.Up till to now,we have carried out three experiments on the spherical hohlraum with 2 LEHs on Shenguang(SG)laser facilities,including demonstration of improving laser transport by using the cylindrical LEHs in the spherical hohlraums,spherical hohlraum energetics on the SGIII prototype laser facility,and comparisons of laser plasma instabilities between the spherical hohlraums and the cylindrical hohlraums on the SGIII laser facility.展开更多
We present our recent laser-plasmas instability(LPI)comparison experiment at the SGIII laser facility between the spherical and cylindrical hohlraums.Three kinds of filling are considered:vacuum,gas-filling with or wi...We present our recent laser-plasmas instability(LPI)comparison experiment at the SGIII laser facility between the spherical and cylindrical hohlraums.Three kinds of filling are considered:vacuum,gas-filling with or without a capsule inside.A spherical hohlraum of 3.6 mm in diameter,and a cylindrical hohlraum of 2.4 mm?4.3 mm are used.The capsule diameter is 0.96 mm.A flat-top laser pulse with 3 ns duration and up to 92.73 kJ energy is used.The experiment has shown that the LPI level in the spherical hohlraum is close to that of the outer beam in the cylindrical hohlraum,while much lower than that of the inner beam.The experiment is further simulated by using our 2-dimensional radiation hydrodynamic code LARED-Integration,and the laser back-scattering fraction and the stimulated Raman scatter(SRS)spectrum are post-processed by the high efficiency code of laser interaction with plasmas HLIP.According to the simulation,the plasma waves are strongly damped and the SRS is mainly developed at the plasma conditions of electron density from 0.08 n_(c) to 0.1 n_(c) and electron temperature from 1.5 keV to 2.0 keV inside the hohlraums.However,obvious differences between the simulation and experiment are found,such as that the SRS back-scattering is underestimated,and the numerical SRS spectrum peaks at a larger wavelength and at a later time than the data.These dif-ferences indicate that the development of a 3D radiation hydrodynamic code,with more accurate physics models,is mandatory for spherical hohlraum study.展开更多
Molecular dynamics simulations are performed to gain insights into the structural and vibrational properties of interface between porous and fused silica.The Si–O bonds formed in the interface exhibit the same length...Molecular dynamics simulations are performed to gain insights into the structural and vibrational properties of interface between porous and fused silica.The Si–O bonds formed in the interface exhibit the same lengths as the bulk material, whereas the coordination defects in the interface are at an intermediate level as compared with the dense and porous structures.Clustered bonds are identified from the interface, which are associated with the reorganization of the silica surface.The bond angle distributions show that the O–Si–O bond angles keep the average value of 109°, whereas the Si–O–Si angles of the interface present in a similar manner to those in porous silica.Despite the slight structural differences, similarities in the vibrations are observed, which could further demonstrate the stability of porous silica films coated on the fused silica.展开更多
Optical Thomson scattering(OTS)diagnostics have been continuously developed on a series of large laser facilities for inertial confinement fusion(ICF)research in China.We review recent progress in the use of OTS diagn...Optical Thomson scattering(OTS)diagnostics have been continuously developed on a series of large laser facilities for inertial confinement fusion(ICF)research in China.We review recent progress in the use of OTS diagnostics to study the internal plasma conditions of ICF gas-filled hohlraums.We establish the predictive capability for experiments by calculating the time-resolved Thomson scattering spectra based on the 2D radiation-hydrodynamic code LARED,and we explore the fitting method for the measured spectra.A typical experiment with a simplified cylindrical hohlraum is conducted on a 10 kJ-level laser facility,and the plasma evolution around the laser entrance hole is analyzed.The dynamic effects of the blast wave from the covering membrane and the convergence of shocks on the hohlraum axis are observed,and the experimental results agree well with those of simulations.Another typical experiment with an octahedral spherical hohlraum is conducted on a 100 kJ-level laser facility,and the plasma evolution at the hohlraum center is analyzed.A discrepancy appears between experiment and simulation as the electron temperature rises,indicating the occurrence of nonlocal thermal conduction.展开更多
SG-Ⅲ laser facility is now the largest laser driver for inertial confinement fusion research in China. The whole laser facility can deliver 180 kJ energy and 60 TW power ultraviolet laser onto target, with power bala...SG-Ⅲ laser facility is now the largest laser driver for inertial confinement fusion research in China. The whole laser facility can deliver 180 kJ energy and 60 TW power ultraviolet laser onto target, with power balance better than 10%.We review the laser system and introduce the SG-Ⅲ laser performance here.展开更多
Utilizing polarization maintaining photonic crystal fiber(PM-PCF)with the low temperature coefficient of birefringence,a two-dimensional tunable and temperature-insensitive Lyot filter aiming to compensate the frequen...Utilizing polarization maintaining photonic crystal fiber(PM-PCF)with the low temperature coefficient of birefringence,a two-dimensional tunable and temperature-insensitive Lyot filter aiming to compensate the frequency modulation to amplitude modulation(FM-to-AM)conversion in high power laser facility is demonstrated.The Jones matrix is applied to analyze the relationship between optical characteristics of the filter and physical parameters(including amplitude ratio,phase delay,and susceptibility of the birefringence to temperature)of the polarization optical field.Both the transmission peak wavelength and extinction ratio of the spectral transmission are able to be changed simultaneously,hence,it shows more efficient FM-to-AM compensation ability.Besides,the transmission peak shift is about 18pm/°C with the PM-PCF configuration,which is about two orders of magnitude less than the normal polarization maintaining fiber(PMF)configuration.The demonstrated filter presents a practical application potential in large scale laser driven facility.展开更多
A 1178 J near diffraction limited 527 nm laser is realized in a complete closed-loop adaptive optics(AO)controlled off-axis multi-pass amplification laser system.Generated from a fiber laser and amplified by the pre-a...A 1178 J near diffraction limited 527 nm laser is realized in a complete closed-loop adaptive optics(AO)controlled off-axis multi-pass amplification laser system.Generated from a fiber laser and amplified by the pre-amplifier and the main amplifier,a 1053 nm laser beam with the energy of 1900 J is obtained and converted into a 527 nm laser beam by a KDP crystal with 62%conversion efficiency,1178 J and beam quality of 7.93 times the diffraction limit(DL).By using a complete closed-loop AO configuration,the static and dynamic wavefront distortions of the laser system are measured and compensated.After correction,the diameter of the circle enclosing 80%energy is improved remarkably from 7.93DL to 1.29DL.The focal spot is highly concentrated and the 1178 J,527 nm near diffraction limited laser is achieved.展开更多
文摘The third paragraph in Sec.IV REGENERATIVE AMPLIFICATION erroneously states“In other words,the distribution of spectral components is time-dependent,and the spectral distortion in the amplification process will not change the time-domain shape.”
基金support of the National Natural Science Foundation of China(Grant Nos.62075030,62075201,and 11904339)the Sichuan Provincial Project for Outstanding Young Scholars in Science and Technology(Grant No.2020JDJQ0024)。
文摘Broadband low-coherence light is considered to be an effective way to suppress laser plasma instability.Recent studies have demonstrated the ability of low-coherence laser facilities to reduce back-scattering during beam–target coupling.However,to ensure simultaneous low coherence and high energy,complex spectral modulation methods and amplification routes have to be adopted.In this work,we propose the use of a random fiber laser(RFL)as the seed source.The spectral features of this RFL can be carefully tailored to provide a good match with the gain characteristics of the laser amplification medium,thus enabling efficient amplification while maintaining low coherence.First,a theoretical model is constructed to give a comprehensive description of the output characteristics of the spectrum-tailored RFL,after which the designed RFL is experimentally realized as a seed source.Through precise pulse shaping and efficient regenerative amplification,a shaped random laser pulse output of 28 mJ is obtained,which is the first random laser system with megawatt-class peak power that is able to achieve low coherence and efficient spectrum-conformal regenerative amplification.
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 Fundamental Research Program of China(Contact No.11475033 and 11405011)CAEP(Contact No.2013A0102002).
文摘In this paper,we give a review of our theoretical and experimental progress in octahedral spherical hohlraum study.From our theoretical study,the octahedral spherical hohlraums with 6 Laser Entrance Holes(LEHs)of octahedral symmetry have robust high symmetry during the capsule implosion at hohlraum-to-capsule radius ratio larger than 3.7.In addition,the octahedral spherical hohlraums also have potential superiority on low backscattering without supplementary technology.We studied the laser arrangement and constraints of the octahedral spherical hohlraums,and gave a design on the laser arrangement for ignition octahedral hohlraums.As a result,the injection angle of laser beams of 50°-60°was proposed as the optimum candidate range for the octahedral spherical hohlraums.We proposed a novel octahedral spherical hohlraum with cylindrical LEHs and LEH shields,in order to increase the laser coupling efficiency and improve the capsule symmetry and to mitigate the influence of the wall blowoff on laser transport.We studied on the sensitivity of the octahedral spherical hohlraums to random errors and compared the sensitivity among the octahedral spherical hohlraums,the rugby hohlraums and the cylindrical hohlraums,and the results show that the octahedral spherical hohlraums are robust to these random errors while the cylindrical hohlraums are the most sensitive.Up till to now,we have carried out three experiments on the spherical hohlraum with 2 LEHs on Shenguang(SG)laser facilities,including demonstration of improving laser transport by using the cylindrical LEHs in the spherical hohlraums,spherical hohlraum energetics on the SGIII prototype laser facility,and comparisons of laser plasma instabilities between the spherical hohlraums and the cylindrical hohlraums on the SGIII laser facility.
基金This work is supported by the National Natural Science Foundation of China under grants Nos.11405011 and 11475033.
文摘We present our recent laser-plasmas instability(LPI)comparison experiment at the SGIII laser facility between the spherical and cylindrical hohlraums.Three kinds of filling are considered:vacuum,gas-filling with or without a capsule inside.A spherical hohlraum of 3.6 mm in diameter,and a cylindrical hohlraum of 2.4 mm?4.3 mm are used.The capsule diameter is 0.96 mm.A flat-top laser pulse with 3 ns duration and up to 92.73 kJ energy is used.The experiment has shown that the LPI level in the spherical hohlraum is close to that of the outer beam in the cylindrical hohlraum,while much lower than that of the inner beam.The experiment is further simulated by using our 2-dimensional radiation hydrodynamic code LARED-Integration,and the laser back-scattering fraction and the stimulated Raman scatter(SRS)spectrum are post-processed by the high efficiency code of laser interaction with plasmas HLIP.According to the simulation,the plasma waves are strongly damped and the SRS is mainly developed at the plasma conditions of electron density from 0.08 n_(c) to 0.1 n_(c) and electron temperature from 1.5 keV to 2.0 keV inside the hohlraums.However,obvious differences between the simulation and experiment are found,such as that the SRS back-scattering is underestimated,and the numerical SRS spectrum peaks at a larger wavelength and at a later time than the data.These dif-ferences indicate that the development of a 3D radiation hydrodynamic code,with more accurate physics models,is mandatory for spherical hohlraum study.
文摘Molecular dynamics simulations are performed to gain insights into the structural and vibrational properties of interface between porous and fused silica.The Si–O bonds formed in the interface exhibit the same lengths as the bulk material, whereas the coordination defects in the interface are at an intermediate level as compared with the dense and porous structures.Clustered bonds are identified from the interface, which are associated with the reorganization of the silica surface.The bond angle distributions show that the O–Si–O bond angles keep the average value of 109°, whereas the Si–O–Si angles of the interface present in a similar manner to those in porous silica.Despite the slight structural differences, similarities in the vibrations are observed, which could further demonstrate the stability of porous silica films coated on the fused silica.
基金This work is supported by the National Key R&D Program of China(Grant No.2017YFA0403300)the Science Challenge Project(No.TZ2016005)the Natural Science Foundation of China(Grant Nos.11435011,11505168,and 11705180).
文摘Optical Thomson scattering(OTS)diagnostics have been continuously developed on a series of large laser facilities for inertial confinement fusion(ICF)research in China.We review recent progress in the use of OTS diagnostics to study the internal plasma conditions of ICF gas-filled hohlraums.We establish the predictive capability for experiments by calculating the time-resolved Thomson scattering spectra based on the 2D radiation-hydrodynamic code LARED,and we explore the fitting method for the measured spectra.A typical experiment with a simplified cylindrical hohlraum is conducted on a 10 kJ-level laser facility,and the plasma evolution around the laser entrance hole is analyzed.The dynamic effects of the blast wave from the covering membrane and the convergence of shocks on the hohlraum axis are observed,and the experimental results agree well with those of simulations.Another typical experiment with an octahedral spherical hohlraum is conducted on a 100 kJ-level laser facility,and the plasma evolution at the hohlraum center is analyzed.A discrepancy appears between experiment and simulation as the electron temperature rises,indicating the occurrence of nonlocal thermal conduction.
文摘SG-Ⅲ laser facility is now the largest laser driver for inertial confinement fusion research in China. The whole laser facility can deliver 180 kJ energy and 60 TW power ultraviolet laser onto target, with power balance better than 10%.We review the laser system and introduce the SG-Ⅲ laser performance here.
基金This work was supported by the Science and Technology Major Project of Guangxi(Grant No.AA18118032)Laser Fusion Research Center Funds for Young Talents(Grant No.RCFCZ3-2019-7).
文摘Utilizing polarization maintaining photonic crystal fiber(PM-PCF)with the low temperature coefficient of birefringence,a two-dimensional tunable and temperature-insensitive Lyot filter aiming to compensate the frequency modulation to amplitude modulation(FM-to-AM)conversion in high power laser facility is demonstrated.The Jones matrix is applied to analyze the relationship between optical characteristics of the filter and physical parameters(including amplitude ratio,phase delay,and susceptibility of the birefringence to temperature)of the polarization optical field.Both the transmission peak wavelength and extinction ratio of the spectral transmission are able to be changed simultaneously,hence,it shows more efficient FM-to-AM compensation ability.Besides,the transmission peak shift is about 18pm/°C with the PM-PCF configuration,which is about two orders of magnitude less than the normal polarization maintaining fiber(PMF)configuration.The demonstrated filter presents a practical application potential in large scale laser driven facility.
基金the National Natural Science Foundation of China(Nos.61775199 and 61775112).
文摘A 1178 J near diffraction limited 527 nm laser is realized in a complete closed-loop adaptive optics(AO)controlled off-axis multi-pass amplification laser system.Generated from a fiber laser and amplified by the pre-amplifier and the main amplifier,a 1053 nm laser beam with the energy of 1900 J is obtained and converted into a 527 nm laser beam by a KDP crystal with 62%conversion efficiency,1178 J and beam quality of 7.93 times the diffraction limit(DL).By using a complete closed-loop AO configuration,the static and dynamic wavefront distortions of the laser system are measured and compensated.After correction,the diameter of the circle enclosing 80%energy is improved remarkably from 7.93DL to 1.29DL.The focal spot is highly concentrated and the 1178 J,527 nm near diffraction limited laser is achieved.
