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
The interaction of high-power laser pulses with undercritical foams produced by different techniques but with the same average density is studied at the PALS laser facility.The spatial-temporal evolution of X-ray emis...The interaction of high-power laser pulses with undercritical foams produced by different techniques but with the same average density is studied at the PALS laser facility.The spatial-temporal evolution of X-ray emission is observed using an X-ray streak camera,electron and ion temperatures are measured by X-ray spectroscopy,and hot-electron production is characterized by monochromatic X-ray imaging.Transmission of a femtosecond laser probe pulse through foams is observed in the near and far fields.In spite of large differences in pore size and foam structure,the velocity of ionization front propagation is quite similar for all the foams studied and is slower than that in a homogeneous material of the same average density.The ion temperature in the plasma behind the ionization front is a few times higher than the electron temperature.Hot-electron production in plastic foams with small pores is strongly suppressed compared with that in solid targets,whereas in foams produced by additive manufacturing,it is significantly increased to the level observed in bare copper foil targets.展开更多
In indirect-driven laser fusion experiments,the movement of the laser absorption layer will distort the radiation uniformity on the capsule.The gold foam has advantages in symmetry control and lowering wall plasma blo...In indirect-driven laser fusion experiments,the movement of the laser absorption layer will distort the radiation uniformity on the capsule.The gold foam has advantages in symmetry control and lowering wall plasma blowoff when used in an inertial confinement fusion(ICF)hohlraum.This work investigates the motion of the laser absorption cutoff position using lowdensity foam gold walls.It is found that the motion of the laser absorption cutoff position can be significantly mitigated through optimal initial low density,tailored to a specific laser shape.For a short square laser pulse,the laser absorption cutoff position remains almost stationary at an initial density of approximately 0.6 g cm^(-3).For a long-shaped laser pulse,the minimal motion of the laser absorption cutoff position is observed at an initial density of about 0.1 g cm^(-3).This approach allows for the adjustment of the symmetry of the hohlraum radiation source.The insights gained from this study serve as a crucial reference for optimizing the hohlraum wall density.展开更多
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 the Center of Advanced Applied Sciences(CAAS)Project No.(CZ.02.1.01/0.0/0.0/16019/0000778)from the European Regional Development Fundalso supported in part by the Czech Technical University in Prague Project No.SGS22/184/OHK4/3T/14+1 种基金partial funding via EUROfusion Enabling Research Project No.AWP24-ENR-03-CEA-02“Foams as a pathway to energy from high gain direct drive ignition,”within the framework of the EUROfusion Consortium,funded by the European Union via the Euratom Research and Training Program(Grant Agreement No.101052200-EUROfusion)the Czech Ministry of Education,Youth and Sports(CMEYS)for funding the operation of the PALS facility(Grant No.LM2023068)。
文摘The interaction of high-power laser pulses with undercritical foams produced by different techniques but with the same average density is studied at the PALS laser facility.The spatial-temporal evolution of X-ray emission is observed using an X-ray streak camera,electron and ion temperatures are measured by X-ray spectroscopy,and hot-electron production is characterized by monochromatic X-ray imaging.Transmission of a femtosecond laser probe pulse through foams is observed in the near and far fields.In spite of large differences in pore size and foam structure,the velocity of ionization front propagation is quite similar for all the foams studied and is slower than that in a homogeneous material of the same average density.The ion temperature in the plasma behind the ionization front is a few times higher than the electron temperature.Hot-electron production in plastic foams with small pores is strongly suppressed compared with that in solid targets,whereas in foams produced by additive manufacturing,it is significantly increased to the level observed in bare copper foil targets.
基金supported by the Presidential Foundation of China Academy of Engineering Physics (No. YZJJLX 2018011)National Natural Science Foundation of China (Nos. 11775204, 11734013, 12105269 and 12004351)
文摘In indirect-driven laser fusion experiments,the movement of the laser absorption layer will distort the radiation uniformity on the capsule.The gold foam has advantages in symmetry control and lowering wall plasma blowoff when used in an inertial confinement fusion(ICF)hohlraum.This work investigates the motion of the laser absorption cutoff position using lowdensity foam gold walls.It is found that the motion of the laser absorption cutoff position can be significantly mitigated through optimal initial low density,tailored to a specific laser shape.For a short square laser pulse,the laser absorption cutoff position remains almost stationary at an initial density of approximately 0.6 g cm^(-3).For a long-shaped laser pulse,the minimal motion of the laser absorption cutoff position is observed at an initial density of about 0.1 g cm^(-3).This approach allows for the adjustment of the symmetry of the hohlraum radiation source.The insights gained from this study serve as a crucial reference for optimizing the hohlraum wall density.
