Blast-wave-driven hydrodynamic instabilities are studied in the presence of a background B-field through experiments and simulations in the high-energy-density(HED)physics regime.In experiments conducted at the Labora...Blast-wave-driven hydrodynamic instabilities are studied in the presence of a background B-field through experiments and simulations in the high-energy-density(HED)physics regime.In experiments conducted at the Laboratoire pour l’utilisation des lasers intenses(LULI),a laserdriven shock-tube platform was used to generate a hydrodynamically unstable interface with a prescribed sinusoidal surface perturbation,and short-pulse x-ray radiography was used to characterize the instability growth with and without a 10-T B-field.The LULI experiments were modeled in FLASH using resistive and ideal magnetohydrodynamics(MHD),and comparing the experiments and simulations suggests that the Spitzer model implemented in FLASH is necessary and sufficient for modeling these planar systems.These results suggest insufficient amplification of the seed B-field,due to resistive diffusion,to alter the hydrodynamic behavior.Although the ideal-MHD simulations did not represent the experiments accurately,they suggest that similar HED systems with dynamic plasma-β(=2μ_(0)ρv^(2)/B^(2))values of less than∼100 can reduce the growth of blast-wave-driven Rayleigh–Taylor instabilities.These findings validate the resistive-MHD FLASH modeling that is being used to design future experiments for studying B-field effects in HED plasmas.展开更多
Experiments have identified the Rayleigh–Taylor(RT)instability as one of the greatest obstacles to achieving inertial confinement fusion.Consequently,mitigation strategies to reduce RT growth and fuel–ablator mixing...Experiments have identified the Rayleigh–Taylor(RT)instability as one of the greatest obstacles to achieving inertial confinement fusion.Consequently,mitigation strategies to reduce RT growth and fuel–ablator mixing in the hotspot during the deceleration phase of the implosion are of great interest.In this work,the effect of seed magnetic fields on deceleration-phase RT growth are studied in planar and cylindrical geometries under conditions relevant to the National Ignition Facility(NIF)and Omega experiments.The magnetohydrodynamic(MHD)and resistive-MHD capabilities of the FLASH code are used to model imploding cylinders and planar blast-wave-driven targets.Realistic target and laser parameters are presented that suggest the occurrence of morphological differences in late-time RT evolution in the cylindrical NIF case and a measurable difference in spike height of single-mode growth in the planar NIF case.The results of this study indicate the need for target designs to utilize an RT-unstable foam–foam interface in order to achieve sufficient magnetic field amplification to alter RT evolution.Benchmarked FLASH simulations are used to study these magnetic field effects in both resistive and ideal MHD.展开更多
文摘Blast-wave-driven hydrodynamic instabilities are studied in the presence of a background B-field through experiments and simulations in the high-energy-density(HED)physics regime.In experiments conducted at the Laboratoire pour l’utilisation des lasers intenses(LULI),a laserdriven shock-tube platform was used to generate a hydrodynamically unstable interface with a prescribed sinusoidal surface perturbation,and short-pulse x-ray radiography was used to characterize the instability growth with and without a 10-T B-field.The LULI experiments were modeled in FLASH using resistive and ideal magnetohydrodynamics(MHD),and comparing the experiments and simulations suggests that the Spitzer model implemented in FLASH is necessary and sufficient for modeling these planar systems.These results suggest insufficient amplification of the seed B-field,due to resistive diffusion,to alter the hydrodynamic behavior.Although the ideal-MHD simulations did not represent the experiments accurately,they suggest that similar HED systems with dynamic plasma-β(=2μ_(0)ρv^(2)/B^(2))values of less than∼100 can reduce the growth of blast-wave-driven Rayleigh–Taylor instabilities.These findings validate the resistive-MHD FLASH modeling that is being used to design future experiments for studying B-field effects in HED plasmas.
基金This work was supported by the Office of Science of the U.S.Department of Energy under Award Nos.DE-SC0018993,DE-SC0016515,and DE-SC0022319the High Energy Density Laboratory Plasmas subprogram of the Fusion Energy Sciences program and under Award No.DE-SC0020055 by the Financial Assistance ProgramThis work was also supported through a Los Alamos National Laboratory subcontract to Virginia Tech under Contract No.463281.
文摘Experiments have identified the Rayleigh–Taylor(RT)instability as one of the greatest obstacles to achieving inertial confinement fusion.Consequently,mitigation strategies to reduce RT growth and fuel–ablator mixing in the hotspot during the deceleration phase of the implosion are of great interest.In this work,the effect of seed magnetic fields on deceleration-phase RT growth are studied in planar and cylindrical geometries under conditions relevant to the National Ignition Facility(NIF)and Omega experiments.The magnetohydrodynamic(MHD)and resistive-MHD capabilities of the FLASH code are used to model imploding cylinders and planar blast-wave-driven targets.Realistic target and laser parameters are presented that suggest the occurrence of morphological differences in late-time RT evolution in the cylindrical NIF case and a measurable difference in spike height of single-mode growth in the planar NIF case.The results of this study indicate the need for target designs to utilize an RT-unstable foam–foam interface in order to achieve sufficient magnetic field amplification to alter RT evolution.Benchmarked FLASH simulations are used to study these magnetic field effects in both resistive and ideal MHD.
