We put forward a new design of a compact beam transport system for intense laser-driven proton therapy,where instead of using conventional pulsed solenoids,our design relies on a helical coil irradiated by a nanosecon...We put forward a new design of a compact beam transport system for intense laser-driven proton therapy,where instead of using conventional pulsed solenoids,our design relies on a helical coil irradiated by a nanosecond laser pulse to generate strong magnetic fields for focusing protons.A pair of dipole magnets and apertures are employed to further filter protons with large divergences and low energies.Our numerical studies combine particle-in-cell simulations for laser-plasma interaction to generate high-energy monoenergetic proton beams,finite element analysis for evaluating the magnetic field distribution inside the coil,and MonteCarlo simulations for beam transport and energy deposition.Our results show that with this design,a spread-out Bragg peak in a range of several centimeters to a deep-seated tumor with a dose of approximately 16.5 cGy and fluctuation around 2% can be achieved.The instantaneous dose rate reaches up to 10^(9)Gy/s,holding the potential for future FLASH radiotherapy research.展开更多
Warm dense plasmas are crucial for high-energy-density physics and inertial confinement fusion research.Experiments involving laser-irradiated copper(Cu)foil were performed at the Shenguang-II facility.A highly orient...Warm dense plasmas are crucial for high-energy-density physics and inertial confinement fusion research.Experiments involving laser-irradiated copper(Cu)foil were performed at the Shenguang-II facility.A highly oriented pyrolytic graphite crystal spectrometer measured the time-integrated spectral distribution of Cu under varying laser intensities.Using the two-dimensional radiation-hydrodynamics code FLASH and the spectral analysis code FLYCHK,we simulated the temporal evolution of plasma density and temperature distributions,as well as the emission intensities of spectral lines at different temperatures and densities.The simulation results revealed that the two-electron satellite lines(J)and the resonance line(W)emissions of Cu originate predominantly from the radiation region near the critical density surface,with a density range from approximately 0.5 nc to 1.0 nc,and radiate primarily during the laser irradiation period.By analyzing the J/W intensity ratio of the measured spectral lines,we estimated the electron temperatures near the critical-density surface under different laser intensities.展开更多
Strong multi-kilotesla magnetic fields have various applications in high-energy density science and laboratory astrophysics, but they are not readily available. In our previous work [Y. Shi et al., Phys. Rev. Lett. 13...Strong multi-kilotesla magnetic fields have various applications in high-energy density science and laboratory astrophysics, but they are not readily available. In our previous work [Y. Shi et al., Phys. Rev. Lett. 130, 155101(2023)], we developed a novel approach for generating such fields using multiple conventional laser beams with a twist in the pointing direction. This method is particularly well-suited for multi-kilojoule petawatt-class laser systems like SG-Ⅱ UP, which are designed with multiple linearly polarized beamlets. Utilizing three-dimensional kinetic particle-in-cell simulations, we examine critical factors for a proof-of-principle experiment, such as laser polarization, relative pulse delay,phase offset, pointing stability, and target configuration, and their impact on magnetic field generation. Our general conclusion is that the approach is very robust and can be realized under a wide range of laser parameters and plasma conditions. We also provide an in-depth analysis of the axial magnetic field configuration, azimuthal electron current, and electron and ion orbital angular momentum densities.Supported by a simple model, our analysis shows that the axial magnetic field decays owing to the expansion of hot electrons.展开更多
Recent experiments at the National Ignition Facility and theoretical modeling suggest that side stimulated Raman scattering(SSRS)instability could reduce laser–plasma coupling and generate considerable fluxes of supr...Recent experiments at the National Ignition Facility and theoretical modeling suggest that side stimulated Raman scattering(SSRS)instability could reduce laser–plasma coupling and generate considerable fluxes of suprathermal hot electrons under interaction conditions envisaged for direct-drive schemes for inertial confinement fusion.Nonetheless,SSRS remains to date one of the least understood parametric instabilities.Here,we report the first angularly and spectrally resolved measurements of scattered light at laser intensities relevant for the shock ignition scheme(I×10^(16)W/cm^(2)),showing significant SSRS growth in the direction perpendicular to the laser polarization.Modification of the focal spot shape and orientation,obtained by using two different random phase plates,and of the density gradient of the plasma,by utilizing exploding foil targets of different thicknesses,clearly reveals a different dependence of backward SRS(BSRS)and SSRS on experimental parameters.While convective BSRS scales with plasma density scale length,as expected by linear theory,the growth of SSRS depends on the spot extension in the direction perpendicular to laser polarization.Our analysis therefore demonstrates that under current experimental conditions,with density scale lengths L_(n)≈60–120μm and spot sizes FWHM≈40–100μm,SSRS is limited by laser beam size rather than by the density scale length of the plasma.展开更多
In this paper,a novel Ce(Gd2 Y)Al5O12/Ce:Y3Al5O12(Ce:GYAG/Ce:YAG)composite scintillation ceramic was designed and fabricated by a solid-state reaction method.The phase,luminescence and scintillation properties were in...In this paper,a novel Ce(Gd2 Y)Al5O12/Ce:Y3Al5O12(Ce:GYAG/Ce:YAG)composite scintillation ceramic was designed and fabricated by a solid-state reaction method.The phase,luminescence and scintillation properties were investigated.The Ce:GYAG/Ce:YAG composite ceramic consisting of two-phase has a broad emission band ranging from 500 to 750 nm.The total mass attenuation coefficient of Ce:GYAG/Ce:YAG is 0.3864 cm^-1,in between those of Ce:YAG and Ce:GYAG ceramics.In addition,the composite ceramic had a high light yield of 20430 ph/MeV.By controlling the ratio of GYAG and YAG,the composite ceramic can realize a spectrum design and total mass attenuation coefficient control to meet the requirements for wide-X-ray-energy-range detectors.展开更多
A new scheme of multibeam Raman amplification(MRA)is proposed in virtue of the collective mode by sharing a common scattered light.Multiple laser beams can provide a higher growth rate,but the overlapping region limit...A new scheme of multibeam Raman amplification(MRA)is proposed in virtue of the collective mode by sharing a common scattered light.Multiple laser beams can provide a higher growth rate,but the overlapping region limits the amplification length.We suggest to use a finite-duration seed to facilitate MRA in a short distance.Through two-dimensional particle-in-cell simulations,we find that two-beam Raman amplification has a much higher growth rate than that of singlebeam one.This growth rate depends on the initial seed amplitude,electron temperature,and seed duration.An empirical criterion,γ0τc=1,whereγ0 is the theoretical growth rate of MRA,is used to choose a proper duration for a higher growth rate.After a total amplification length of 320µm,the two-beam Raman amplification shows nonlinear features of pulse compression and a bow-shape wave front,indicating that the amplification has finally entered the self-similar regime.展开更多
Porous Pt thin films were prepared on carbon papers by a single-step ultra-high dc magnetron sputtering method to obtain ideal electrodes for proton exchange membrane fuel cells.The platinum loading of the electrocata...Porous Pt thin films were prepared on carbon papers by a single-step ultra-high dc magnetron sputtering method to obtain ideal electrodes for proton exchange membrane fuel cells.The platinum loading of the electrocatalyst layer is controlled at about 0.1 mg·cm^(-2).Structural characteristics and catalytic activities of the films were analyzed by scanning electron microscopy,atomic force microscopy,X-ray diffraction,cyclic voltammetry,and stress durability testing methods.The effect of treatment conditions of a substrate on the structural and performance characteristics of the catalytic films was shown as well.Films produced on acid-treated carbon papers at the argon pressure of 0.01 mbar possessed a homogeneous,highly developed surface along with a porous structure.Compared to Pt/TCPW(Toray carbon papers soaked in ultrapure water)electrodes,the film obtained on the acid-treated substrate had a larger electrochemical surface area(163.33 m^(2)·g^(-1))and exhibited better catalytic stability and durability due to a porous structure as a result of Pt particle accumulation.展开更多
Based on the numerical solution of the time-dependent Dirac equation,we propose a method to observe in real time the ac Stark shift of a vacuum driven by an ultra-intense laser field.By overlapping the ultra-intense p...Based on the numerical solution of the time-dependent Dirac equation,we propose a method to observe in real time the ac Stark shift of a vacuum driven by an ultra-intense laser field.By overlapping the ultra-intense pump pulse with another zeptosecond probe pulse whose photon energy is smaller than 2mc^(2),electron–positron pair creation can be controlled by tuning the time delay between the pump and probe pulses.Since the pair creation rate depends sensitively on the instantaneous vacuum potential,one can reconstruct the ac Stark shift of the vacuum potential according to the time-delay-dependent pair creation rate.展开更多
Stimulated Raman scattering(SRS)excited by incoherent light is studied via particle-in-cell simulations.It is shown that a large bandwidth of incoherent light can reduce the growth of SRS and electron heating consider...Stimulated Raman scattering(SRS)excited by incoherent light is studied via particle-in-cell simulations.It is shown that a large bandwidth of incoherent light can reduce the growth of SRS and electron heating considerably in the linear stage.However,different components of the incoherent light can be coupled by the Langmuir waves,so that stimulated Raman backward scattering can develop.When the bandwidth of incoherent light is larger than the Langmuir wave frequency,forward SRS can be seeded between different components of the incoherent light.The incoherent light can only increase the time duration for nonlinear saturation but cannot diminish the saturation level obviously.展开更多
基金supported by the National Key R&D Program of China(Nos.2022YFA1603200 and 2022YFA1603201)National Natural Science Foundation of China(Nos.12135001,11921006,12475243 and 11825502)+1 种基金Strategic Priority Research Program of CAS(No.XDA25050900)support from the National Natural Science Funds for Distinguished Young Scholar(No.11825502)。
文摘We put forward a new design of a compact beam transport system for intense laser-driven proton therapy,where instead of using conventional pulsed solenoids,our design relies on a helical coil irradiated by a nanosecond laser pulse to generate strong magnetic fields for focusing protons.A pair of dipole magnets and apertures are employed to further filter protons with large divergences and low energies.Our numerical studies combine particle-in-cell simulations for laser-plasma interaction to generate high-energy monoenergetic proton beams,finite element analysis for evaluating the magnetic field distribution inside the coil,and MonteCarlo simulations for beam transport and energy deposition.Our results show that with this design,a spread-out Bragg peak in a range of several centimeters to a deep-seated tumor with a dose of approximately 16.5 cGy and fluctuation around 2% can be achieved.The instantaneous dose rate reaches up to 10^(9)Gy/s,holding the potential for future FLASH radiotherapy research.
基金Project supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDA25051000,XDA25010100,XDA25010300,XDA25030100,and XDA25030200)。
文摘Warm dense plasmas are crucial for high-energy-density physics and inertial confinement fusion research.Experiments involving laser-irradiated copper(Cu)foil were performed at the Shenguang-II facility.A highly oriented pyrolytic graphite crystal spectrometer measured the time-integrated spectral distribution of Cu under varying laser intensities.Using the two-dimensional radiation-hydrodynamics code FLASH and the spectral analysis code FLYCHK,we simulated the temporal evolution of plasma density and temperature distributions,as well as the emission intensities of spectral lines at different temperatures and densities.The simulation results revealed that the two-electron satellite lines(J)and the resonance line(W)emissions of Cu originate predominantly from the radiation region near the critical density surface,with a density range from approximately 0.5 nc to 1.0 nc,and radiate primarily during the laser irradiation period.By analyzing the J/W intensity ratio of the measured spectral lines,we estimated the electron temperatures near the critical-density surface under different laser intensities.
基金support by the National Natural Science Foundation of China(Grant No.12322513)USTC Research Funds of the Double First-Class Initiative+1 种基金CAS Project for Young Scientists in Basic Research(Grant No.YSBR060)supported by the Office of Fusion Energy Sciences under Award No.DE-SC0023423。
文摘Strong multi-kilotesla magnetic fields have various applications in high-energy density science and laboratory astrophysics, but they are not readily available. In our previous work [Y. Shi et al., Phys. Rev. Lett. 130, 155101(2023)], we developed a novel approach for generating such fields using multiple conventional laser beams with a twist in the pointing direction. This method is particularly well-suited for multi-kilojoule petawatt-class laser systems like SG-Ⅱ UP, which are designed with multiple linearly polarized beamlets. Utilizing three-dimensional kinetic particle-in-cell simulations, we examine critical factors for a proof-of-principle experiment, such as laser polarization, relative pulse delay,phase offset, pointing stability, and target configuration, and their impact on magnetic field generation. Our general conclusion is that the approach is very robust and can be realized under a wide range of laser parameters and plasma conditions. We also provide an in-depth analysis of the axial magnetic field configuration, azimuthal electron current, and electron and ion orbital angular momentum densities.Supported by a simple model, our analysis shows that the axial magnetic field decays owing to the expansion of hot electrons.
基金financial support from the LASERLAB-EUROPE Access to Research Infrastructure Activity (Application No. 23068)carried out within the framework of EUROfusion Enabling Research Projects AWP21-ENR-01-CEA02 and AWP24-ENR-IFE-02-CEA-02+3 种基金received funding from Euratom Research and Training Programme 2021–2025 under Grant No. 633053supported by the Ministry of Youth and Sports of the Czech Republic [Project No. LM2023068 (PALS RI)]by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Nos. XDA25030200 and XDA25010100)supported by COST (European Cooperation in Science and Technology) through Action CA21128 PROBONO (PROton BOron Nuclear Fusion: from energy production to medical applicatiOns)
文摘Recent experiments at the National Ignition Facility and theoretical modeling suggest that side stimulated Raman scattering(SSRS)instability could reduce laser–plasma coupling and generate considerable fluxes of suprathermal hot electrons under interaction conditions envisaged for direct-drive schemes for inertial confinement fusion.Nonetheless,SSRS remains to date one of the least understood parametric instabilities.Here,we report the first angularly and spectrally resolved measurements of scattered light at laser intensities relevant for the shock ignition scheme(I×10^(16)W/cm^(2)),showing significant SSRS growth in the direction perpendicular to the laser polarization.Modification of the focal spot shape and orientation,obtained by using two different random phase plates,and of the density gradient of the plasma,by utilizing exploding foil targets of different thicknesses,clearly reveals a different dependence of backward SRS(BSRS)and SSRS on experimental parameters.While convective BSRS scales with plasma density scale length,as expected by linear theory,the growth of SSRS depends on the spot extension in the direction perpendicular to laser polarization.Our analysis therefore demonstrates that under current experimental conditions,with density scale lengths L_(n)≈60–120μm and spot sizes FWHM≈40–100μm,SSRS is limited by laser beam size rather than by the density scale length of the plasma.
基金financially supported by the National Natural Science Foundation of China(Nos.61378069,61405221,and 11535010)Youth Innovation Promotion Association of the Chinese Academy of Science(CAS)+2 种基金National Key Research and Development Program of China(SQ2017YFGX010025-03)Interdisciplinary Innovation Team of the CASGeneral Financial Grant from the China Postdoctoral Science Foundation(No.2016M601654)
文摘In this paper,a novel Ce(Gd2 Y)Al5O12/Ce:Y3Al5O12(Ce:GYAG/Ce:YAG)composite scintillation ceramic was designed and fabricated by a solid-state reaction method.The phase,luminescence and scintillation properties were investigated.The Ce:GYAG/Ce:YAG composite ceramic consisting of two-phase has a broad emission band ranging from 500 to 750 nm.The total mass attenuation coefficient of Ce:GYAG/Ce:YAG is 0.3864 cm^-1,in between those of Ce:YAG and Ce:GYAG ceramics.In addition,the composite ceramic had a high light yield of 20430 ph/MeV.By controlling the ratio of GYAG and YAG,the composite ceramic can realize a spectrum design and total mass attenuation coefficient control to meet the requirements for wide-X-ray-energy-range detectors.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA25050700)the National Natural Science Foundation of China(Grant No.11805062)+2 种基金Science Challenge Project(Grant No.TZ2016005)Natural Science Foundation of Hunan Province,China(Grant Nos.2020JJ5029 and 2020JJ5031)the Project of Science and Technology on Plasma Physics Laboratory(Grant No.6142A04190111)。
文摘A new scheme of multibeam Raman amplification(MRA)is proposed in virtue of the collective mode by sharing a common scattered light.Multiple laser beams can provide a higher growth rate,but the overlapping region limits the amplification length.We suggest to use a finite-duration seed to facilitate MRA in a short distance.Through two-dimensional particle-in-cell simulations,we find that two-beam Raman amplification has a much higher growth rate than that of singlebeam one.This growth rate depends on the initial seed amplitude,electron temperature,and seed duration.An empirical criterion,γ0τc=1,whereγ0 is the theoretical growth rate of MRA,is used to choose a proper duration for a higher growth rate.After a total amplification length of 320µm,the two-beam Raman amplification shows nonlinear features of pulse compression and a bow-shape wave front,indicating that the amplification has finally entered the self-similar regime.
基金Funded by the Doctoral Fund of Southwest University of Science and Technology(Nos.19zx7131 and 18zx7132)the Applied Fundamental Research Projects of Science and Technology Department of Sichuan Province(No.2020YJ0333)+1 种基金the Science and Technology on Plasma Physics Laboratory:6142A04180405Science and Technology on Plasma Physics Laboratory:ZY2018-07。
文摘Porous Pt thin films were prepared on carbon papers by a single-step ultra-high dc magnetron sputtering method to obtain ideal electrodes for proton exchange membrane fuel cells.The platinum loading of the electrocatalyst layer is controlled at about 0.1 mg·cm^(-2).Structural characteristics and catalytic activities of the films were analyzed by scanning electron microscopy,atomic force microscopy,X-ray diffraction,cyclic voltammetry,and stress durability testing methods.The effect of treatment conditions of a substrate on the structural and performance characteristics of the catalytic films was shown as well.Films produced on acid-treated carbon papers at the argon pressure of 0.01 mbar possessed a homogeneous,highly developed surface along with a porous structure.Compared to Pt/TCPW(Toray carbon papers soaked in ultrapure water)electrodes,the film obtained on the acid-treated substrate had a larger electrochemical surface area(163.33 m^(2)·g^(-1))and exhibited better catalytic stability and durability due to a porous structure as a result of Pt particle accumulation.
基金supported by the National Natural Science Foundation of China(Grant Nos.12304341 and 11974419)the National Key R&D Program of China(Grant Nos.2021YFA1601700 and 2018YFA0404802)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA25051000).
文摘Based on the numerical solution of the time-dependent Dirac equation,we propose a method to observe in real time the ac Stark shift of a vacuum driven by an ultra-intense laser field.By overlapping the ultra-intense pump pulse with another zeptosecond probe pulse whose photon energy is smaller than 2mc^(2),electron–positron pair creation can be controlled by tuning the time delay between the pump and probe pulses.Since the pair creation rate depends sensitively on the instantaneous vacuum potential,one can reconstruct the ac Stark shift of the vacuum potential according to the time-delay-dependent pair creation rate.
基金This work was supported in part by the National Science Foundation of China(Grant Nos.11421064,11374209,11405107 and 11374210).
文摘Stimulated Raman scattering(SRS)excited by incoherent light is studied via particle-in-cell simulations.It is shown that a large bandwidth of incoherent light can reduce the growth of SRS and electron heating considerably in the linear stage.However,different components of the incoherent light can be coupled by the Langmuir waves,so that stimulated Raman backward scattering can develop.When the bandwidth of incoherent light is larger than the Langmuir wave frequency,forward SRS can be seeded between different components of the incoherent light.The incoherent light can only increase the time duration for nonlinear saturation but cannot diminish the saturation level obviously.
