The physics of laser-plasma interaction is studied on the Shenguang III prototype laser facility under conditions relevant to inertial confinement fusion designs.A sub-millimeter-size underdense hot plasma is created ...The physics of laser-plasma interaction is studied on the Shenguang III prototype laser facility under conditions relevant to inertial confinement fusion designs.A sub-millimeter-size underdense hot plasma is created by ionization of a low-density plastic foam by four high-energy(3.2 kJ)laser beams.An interaction beam is fired with a delay permitting evaluation of the excitation of parametric instabilities at different stages of plasma evolution.Multiple diagnostics are used for plasma characterization,scattered radiation,and accelerated electrons.The experimental results are analyzed with radiation hydrodynamic simulations that take account of foam ionization and homogenization.The measured level of stimulated Raman scattering is almost one order of magnitude larger than that measured in experiments with gasbags and hohlraums on the same installation,possibly because of a greater plasma density.Notable amplification is achieved in high-intensity speckles,indicating the importance of implementing laser temporal smoothing techniques with a large bandwidth for controlling laser propagation and absorption.展开更多
Structural and optical properties of vertically aligned InAs quantum dots (QDs) were embedded in Al0.5Ga0.5As spacer layers. The aligned QDs were grown at 520℃ in the Stranski-Krastanow (S-K) growth mode of molecular...Structural and optical properties of vertically aligned InAs quantum dots (QDs) were embedded in Al0.5Ga0.5As spacer layers. The aligned QDs were grown at 520℃ in the Stranski-Krastanow (S-K) growth mode of molecular beam epitaxy. To impro ve QD characteristics, we employed a size- and density-controlled growth procedu re in the upper layers. Measurements by reflection high-energy electron diffract ion (RHEED) and atomic force microscopy (AFM) showed that both the size and dens ity of the QDs. The temperature dependence of the wavelength-integrated photolum inescence (PL) intensity revealed the InAs QD emission.展开更多
Laser interaction with an ultra-thin pre-structured target is investigated with the help of both two-dimensional and threedimensional particle-in-cell simulations.With the existence of aperiodic structure on the targe...Laser interaction with an ultra-thin pre-structured target is investigated with the help of both two-dimensional and threedimensional particle-in-cell simulations.With the existence of aperiodic structure on the target surface,the laser seems to penetrate through the target at its fundamental frequency even if the plasma density of the target is much higher than the laser’s relativistically critical density.The particle-in-cell simulations show that the transmitted laser energy behind the pre-structured target is increased by about two orders of magnitude compared to that behind the flat target.Theoretical analyses show that the transmitted energy behind the pre-structured target is actually re-emitted by electron’islands’ formed by the surface plasma waves on the target surfaces.In other words,the radiation with the fundamental frequency is actually’surface emission,on the target rear surface.Besides the intensity of the component with the fundamental frequency,the intensity of the high-order harmonics behind the pre-structured target is also much enhanced compared to that behind the flat target.The enhancement of the high-order harmonics is also related to the surface plasma waves generated on the target surfaces.展开更多
Competition among the two-plasmon decay(TPD)of backscattered light of stimulated Raman scattering(SRS),filamentation of the electron-plasma wave(EPW)and forward side SRS is investigated by two-dimensional particlein-c...Competition among the two-plasmon decay(TPD)of backscattered light of stimulated Raman scattering(SRS),filamentation of the electron-plasma wave(EPW)and forward side SRS is investigated by two-dimensional particlein-cell simulations.Our previous work[K.Q.Pan et al.,Nucl.Fusion 58,096035(2018)]showed that in a plasma with the density near 1/10 of the critical density,the backscattered light would excite the TPD,which results in suppression of the backward SRS.However,this work further shows that when the laser intensity is so high(>10^(16)W/cm^(2))that the backward SRS cannot be totally suppressed,filamentation of the EPW and forward side SRS will be excited.Then the TPD of the backscattered light only occurs in the early stage and is suppressed in the latter stage.Electron distribution functions further show that trapped-particle-modulation instability should be responsible for filamentation of the EPW.This research can promote the understanding of hot-electron generation and SRS saturation in inertial confinement fusion experiments.展开更多
基金This project was partially supported by the Advanced Research Using High Intensity Laser Produced Photons and Particles(ADONIS)project(Grant No.CZ.02.1.01/0.0/0.0/16_019/0000789)the CAAS project(Grant No.CZ.02.1.01/0.0/0.0/16_019/0000778)+3 种基金both from the European Regional Development FundThe results of the LQ1606 project were partially obtained with the financial support from the Ministry of Education,Youth and Sports as part of targeted support from the National Programme of Sustainability IIThe authors acknowledge support from the National Natural Science Foundation of China(Grant Nos.11775033,11875241,11975215,11905204,12035002)the Laser Fusion Research Center Funds for Young Talents(Grant No.RCFPD3-2019-6).
文摘The physics of laser-plasma interaction is studied on the Shenguang III prototype laser facility under conditions relevant to inertial confinement fusion designs.A sub-millimeter-size underdense hot plasma is created by ionization of a low-density plastic foam by four high-energy(3.2 kJ)laser beams.An interaction beam is fired with a delay permitting evaluation of the excitation of parametric instabilities at different stages of plasma evolution.Multiple diagnostics are used for plasma characterization,scattered radiation,and accelerated electrons.The experimental results are analyzed with radiation hydrodynamic simulations that take account of foam ionization and homogenization.The measured level of stimulated Raman scattering is almost one order of magnitude larger than that measured in experiments with gasbags and hohlraums on the same installation,possibly because of a greater plasma density.Notable amplification is achieved in high-intensity speckles,indicating the importance of implementing laser temporal smoothing techniques with a large bandwidth for controlling laser propagation and absorption.
基金This work was supported by the Scientific Research Foundation for the Returmed Overseas Chinese Scholars,Education Ministry of China.
文摘Structural and optical properties of vertically aligned InAs quantum dots (QDs) were embedded in Al0.5Ga0.5As spacer layers. The aligned QDs were grown at 520℃ in the Stranski-Krastanow (S-K) growth mode of molecular beam epitaxy. To impro ve QD characteristics, we employed a size- and density-controlled growth procedu re in the upper layers. Measurements by reflection high-energy electron diffract ion (RHEED) and atomic force microscopy (AFM) showed that both the size and dens ity of the QDs. The temperature dependence of the wavelength-integrated photolum inescence (PL) intensity revealed the InAs QD emission.
基金supported by the Science Challenge Project(No.TZ2016005)China Postdoctoral Science Foundation(No.2017M620430)+1 种基金National Natural Science Foundation of China(Nos.11435011,11575035,11705180,and 11875241)the National Basic Research Program of China(No.2013CB834101)
文摘Laser interaction with an ultra-thin pre-structured target is investigated with the help of both two-dimensional and threedimensional particle-in-cell simulations.With the existence of aperiodic structure on the target surface,the laser seems to penetrate through the target at its fundamental frequency even if the plasma density of the target is much higher than the laser’s relativistically critical density.The particle-in-cell simulations show that the transmitted laser energy behind the pre-structured target is increased by about two orders of magnitude compared to that behind the flat target.Theoretical analyses show that the transmitted energy behind the pre-structured target is actually re-emitted by electron’islands’ formed by the surface plasma waves on the target surfaces.In other words,the radiation with the fundamental frequency is actually’surface emission,on the target rear surface.Besides the intensity of the component with the fundamental frequency,the intensity of the high-order harmonics behind the pre-structured target is also much enhanced compared to that behind the flat target.The enhancement of the high-order harmonics is also related to the surface plasma waves generated on the target surfaces.
基金supported by the National Natural Science Foundation of China(Nos.12205274,12275251,12035002,11975215)
文摘Competition among the two-plasmon decay(TPD)of backscattered light of stimulated Raman scattering(SRS),filamentation of the electron-plasma wave(EPW)and forward side SRS is investigated by two-dimensional particlein-cell simulations.Our previous work[K.Q.Pan et al.,Nucl.Fusion 58,096035(2018)]showed that in a plasma with the density near 1/10 of the critical density,the backscattered light would excite the TPD,which results in suppression of the backward SRS.However,this work further shows that when the laser intensity is so high(>10^(16)W/cm^(2))that the backward SRS cannot be totally suppressed,filamentation of the EPW and forward side SRS will be excited.Then the TPD of the backscattered light only occurs in the early stage and is suppressed in the latter stage.Electron distribution functions further show that trapped-particle-modulation instability should be responsible for filamentation of the EPW.This research can promote the understanding of hot-electron generation and SRS saturation in inertial confinement fusion experiments.
