Over the last six years many experiments have been done at the National Ignition Facility to measure the Hugoniot of materials,such asCHplastic at extreme pressures,up to 800 Mbar.The“Gbar”design employs a strong sp...Over the last six years many experiments have been done at the National Ignition Facility to measure the Hugoniot of materials,such asCHplastic at extreme pressures,up to 800 Mbar.The“Gbar”design employs a strong spherically converging shock launched through a solid ball of material using a hohlraum radiation drive.The shock front conditions are characterized using x-ray radiography.In this paper we examine the role of radiation in heating the unshocked material in front of the shock to understand the impact it has on equation of state measurements and how it drives the measured data off the theoretical Hugoniot curve.In particular,the two main sources of radiation heating are the preheating of the unshocked material by the high-energy kilo-electron-volt x-rays in the hohlraum and the heating of the material in front of the shock,as the shocked material becomes hot enough to radiate significantly.Using our model,we estimate that preheating can reach 4 eV in unshocked material,and that radiation heating can begin to drive data off the Hugoniot significantly,as pressures reach above 400 Mb.展开更多
Corrigendum text:There is a misprint in the text of Figs.3 and 4.The text on the bottom part of Figs.3 and 4 should be“100 fs pulse Photoexcitation”and“1 fs pulse Photoexcitation”respectively.This error does not a...Corrigendum text:There is a misprint in the text of Figs.3 and 4.The text on the bottom part of Figs.3 and 4 should be“100 fs pulse Photoexcitation”and“1 fs pulse Photoexcitation”respectively.This error does not affect any conclusions in this work,and it has been corrected in the printed version of the journal.展开更多
Using an X-ray free electron laser(XFEL)at 960 eV to photo-ionize the 1s electron in neutral neon followed by lasing on the 2p-1s transition in singly-ionized neon,an inner-shell X-ray laser was demonstrated at 849 eV...Using an X-ray free electron laser(XFEL)at 960 eV to photo-ionize the 1s electron in neutral neon followed by lasing on the 2p-1s transition in singly-ionized neon,an inner-shell X-ray laser was demonstrated at 849 eV in singly-ionized neon gas several years ago.It took decades to demonstrate this scheme,because it required a very strong X-ray source that could photo-ionize the 1s(K shell)electron in neon on a timescale comparable to the intrinsic Auger lifetime in neon of 2 fs.In this paper,we model the neon inner shell X-ray laser under similar conditions to those used in the XFEL experiments at the SLAC Linac Coherent Light Source(LCLS),and show how we can improve the efficiency of the neon laser and reduce the drive requirements by tuning the XFEL to the 1s-3p transition in neutral neon in order to create gain on the 2p-1s line in neutral neon.We also show how the XFEL could be used to photo-ionize L-shell electrons to drive gain on n=3-2 transitions in singlyionized Ar and Cu plasmas.These bright,coherent,and monochromatic X-ray lasers may prove very useful for doing high-resolution spectroscopy and for studying non-linear process in the X-ray regime.展开更多
基金This work was performed under the auspices of the U.S.Department of Energy by Lawrence Livermore National Laboratory under Contract No.DE-AC52-07NA27344.
文摘Over the last six years many experiments have been done at the National Ignition Facility to measure the Hugoniot of materials,such asCHplastic at extreme pressures,up to 800 Mbar.The“Gbar”design employs a strong spherically converging shock launched through a solid ball of material using a hohlraum radiation drive.The shock front conditions are characterized using x-ray radiography.In this paper we examine the role of radiation in heating the unshocked material in front of the shock to understand the impact it has on equation of state measurements and how it drives the measured data off the theoretical Hugoniot curve.In particular,the two main sources of radiation heating are the preheating of the unshocked material by the high-energy kilo-electron-volt x-rays in the hohlraum and the heating of the material in front of the shock,as the shocked material becomes hot enough to radiate significantly.Using our model,we estimate that preheating can reach 4 eV in unshocked material,and that radiation heating can begin to drive data off the Hugoniot significantly,as pressures reach above 400 Mb.
文摘Corrigendum text:There is a misprint in the text of Figs.3 and 4.The text on the bottom part of Figs.3 and 4 should be“100 fs pulse Photoexcitation”and“1 fs pulse Photoexcitation”respectively.This error does not affect any conclusions in this work,and it has been corrected in the printed version of the journal.
基金performed under the auspices of the U.S.Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344。
文摘Using an X-ray free electron laser(XFEL)at 960 eV to photo-ionize the 1s electron in neutral neon followed by lasing on the 2p-1s transition in singly-ionized neon,an inner-shell X-ray laser was demonstrated at 849 eV in singly-ionized neon gas several years ago.It took decades to demonstrate this scheme,because it required a very strong X-ray source that could photo-ionize the 1s(K shell)electron in neon on a timescale comparable to the intrinsic Auger lifetime in neon of 2 fs.In this paper,we model the neon inner shell X-ray laser under similar conditions to those used in the XFEL experiments at the SLAC Linac Coherent Light Source(LCLS),and show how we can improve the efficiency of the neon laser and reduce the drive requirements by tuning the XFEL to the 1s-3p transition in neutral neon in order to create gain on the 2p-1s line in neutral neon.We also show how the XFEL could be used to photo-ionize L-shell electrons to drive gain on n=3-2 transitions in singlyionized Ar and Cu plasmas.These bright,coherent,and monochromatic X-ray lasers may prove very useful for doing high-resolution spectroscopy and for studying non-linear process in the X-ray regime.
