An experiment on 100 k J laser facility is performed to study the motive features and radiation properties of plasmas from different areas inside gas-filled cylindrical hohlraums.These hohlraums are designed to posses...An experiment on 100 k J laser facility is performed to study the motive features and radiation properties of plasmas from different areas inside gas-filled cylindrical hohlraums.These hohlraums are designed to possess one open end and one laser entrance hole(LEH)with different diameters,which would or not result in the blocking of the LEH.An x-ray streak camera that is set at 16 degrees with respect to the hohlraum axis is applied to acquire the timeresolved x-ray images from the open end.Based on the images,we can study the evolutions of the wall plasma,corona bubble plasma and LEH plasma simultaneously through an equivalent view field of hohlraum interior.Multi-group flat response x-ray detectors are applied to measure the x-ray fluxes.In order to understand these characteristics,our two-dimensional radiation hydrodynamic code is used to simulate the experimental results.For the accuracy of reproduction,dielectronic recombination and two parameter corrections are applied in our code.Based on the comparison between experiments and simulations,we quantitatively understand the blocking process of LEH and the motion effects of other plasmas.The calibrated code is beneficial to design the gas-filled hohlraum in a nearby parameter space,especially the limit size of LEH.展开更多
The first laser–plasma interaction experiment using lasers of eight beams grouped into one octad has been conducted on the Shenguang Octopus facility.Although each beam intensity is below its individual threshold for...The first laser–plasma interaction experiment using lasers of eight beams grouped into one octad has been conducted on the Shenguang Octopus facility.Although each beam intensity is below its individual threshold for stimulated Brillouin backscattering(SBS),collective behaviors are excited to enhance the octad SBS.In particular,when two-color/cone lasers with wavelength separation 0.3 nm are used,the backward SBS reflectivities show novel behavior in which beams of longer wavelength achieve higher SBS gain.This property of SBS can be attributed to the rotation of the wave vectors of common ion acoustic waves due to the competition of detunings between geometrical angle and wavelength separation.This mechanism is confirmed using massively parallel supercomputer simulations with the three-dimensional laser–plasma interaction code LAP3D.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
Wereport experimental research on laser plasma interaction(LPI)conducted in Shenguang laser facilities during the past ten years.The research generally consists of three phases:(1)developing platforms for LPI research...Wereport experimental research on laser plasma interaction(LPI)conducted in Shenguang laser facilities during the past ten years.The research generally consists of three phases:(1)developing platforms for LPI research in mm-scale plasma with limited drive energy,where both gasbag and gas-filled hohlraum targets are tested;(2)studying the effects of beam-smoothing techniques,such as continuous phase plate and polarization smoothing,on the suppression of LPI;and(3)exploring the factors affecting LPI in integrated implosion experiments,which include the laser intensity,gas-fill pressure,size of the laser-entrance hole,and interplay between different beam cones.Results obtained in each phase will be presented and discussed in detail.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
基金supported by National Natural Science Foundation of China(Nos.12075219,12105269 and 12175210)。
文摘An experiment on 100 k J laser facility is performed to study the motive features and radiation properties of plasmas from different areas inside gas-filled cylindrical hohlraums.These hohlraums are designed to possess one open end and one laser entrance hole(LEH)with different diameters,which would or not result in the blocking of the LEH.An x-ray streak camera that is set at 16 degrees with respect to the hohlraum axis is applied to acquire the timeresolved x-ray images from the open end.Based on the images,we can study the evolutions of the wall plasma,corona bubble plasma and LEH plasma simultaneously through an equivalent view field of hohlraum interior.Multi-group flat response x-ray detectors are applied to measure the x-ray fluxes.In order to understand these characteristics,our two-dimensional radiation hydrodynamic code is used to simulate the experimental results.For the accuracy of reproduction,dielectronic recombination and two parameter corrections are applied in our code.Based on the comparison between experiments and simulations,we quantitatively understand the blocking process of LEH and the motion effects of other plasmas.The calibrated code is beneficial to design the gas-filled hohlraum in a nearby parameter space,especially the limit size of LEH.
基金supported by the Natural Science Foundation of China(Grant Nos.11975059,12005021,and 11875241).
文摘The first laser–plasma interaction experiment using lasers of eight beams grouped into one octad has been conducted on the Shenguang Octopus facility.Although each beam intensity is below its individual threshold for stimulated Brillouin backscattering(SBS),collective behaviors are excited to enhance the octad SBS.In particular,when two-color/cone lasers with wavelength separation 0.3 nm are used,the backward SBS reflectivities show novel behavior in which beams of longer wavelength achieve higher SBS gain.This property of SBS can be attributed to the rotation of the wave vectors of common ion acoustic waves due to the competition of detunings between geometrical angle and wavelength separation.This mechanism is confirmed using massively parallel supercomputer simulations with the three-dimensional laser–plasma interaction code LAP3D.
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 was supported by the Science Challenge Project(Grant No.TZ2016005)the Natural Science Foundation of China(Grant Nos.11435011,11875093,and 11875241)the CAEP Foundation(Grant No.PY2019108).
文摘Wereport experimental research on laser plasma interaction(LPI)conducted in Shenguang laser facilities during the past ten years.The research generally consists of three phases:(1)developing platforms for LPI research in mm-scale plasma with limited drive energy,where both gasbag and gas-filled hohlraum targets are tested;(2)studying the effects of beam-smoothing techniques,such as continuous phase plate and polarization smoothing,on the suppression of LPI;and(3)exploring the factors affecting LPI in integrated implosion experiments,which include the laser intensity,gas-fill pressure,size of the laser-entrance hole,and interplay between different beam cones.Results obtained in each phase will be presented and discussed in detail.
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.