Supersonic-to-subsonic transition of a radiation wave observed at the LMJ
| Autor: | C. Courtois, J. Fariaut, R. Rosch, B. Villette, C. Robert, G. Legay, F. Philippe, G. Soullié, Michel Ferri, Isabelle Geoffray, D. Bretheau |
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| Přispěvatelé: | Commissariat à l'énergie atomique et aux énergies alternatives (CEA) |
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Physics
[PHYS]Physics [physics] Shock (fluid dynamics) Astrophysics::High Energy Astrophysical Phenomena Mechanics Radiation Condensed Matter Physics Laser Curvature 01 natural sciences 010305 fluids & plasmas law.invention symbols.namesake Mach number law 0103 physical sciences symbols Supersonic speed 010306 general physics Absorption (electromagnetic radiation) Transonic |
| Zdroj: | Physics of Plasmas Physics of Plasmas, American Institute of Physics, 2021, 28, ⟨10.1063/5.0054288⟩ Physics of Plasmas, 2021, 28, ⟨10.1063/5.0054288⟩ |
| ISSN: | 1070-664X 1089-7674 |
| DOI: | 10.1063/5.0054288⟩ |
| Popis: | International audience; We detail results of an experiment performed at the Laser Mégajoule (LMJ) facilityaimed at studying transition from supersonic radiation front to shock front in a lowdensity CHOBr foam enclosed in a plastic tube driven by thermal emission producedin a laser heated spherical gold cavity. Time resolved 2D hard x-ray radiographyimaging using a Sc source (photon energy at ~ 4.3 keV) is employed to measure thedensity perturbation front position, absorption, curvature and shocked materialcompression (defined as the compressed foam density normalized to its nominal value)from the supersonic to the subsonic regimes of propagation. Between these two regimeswhere compression goes from 1 (limited hydrodynamics) to 4 (strong shock formed), aquick increase of the foam compression is observed at the transition time tHS =6.75±0.75 ns, corresponding to the transient transonic regime (HS means“hydrodynamically separated” and refers to the instant when the shock and the radiationfront physically separate). This time is associated to a foam compression ratio of ~2and a Mach number of the slowing down front below M < 2. Experimental results aresuccessfully compared to 3D hydrodynamics simulations; comparisons never presentedfor that regime in past similar studies to our knowledge. Simulations show that thetransition time tHS is sensitive to the radiation closure of the tube entrance. This closure, which occurs in 3D, affects the amount of x-ray energy coupled from the laser heatedcavity to the CHOBr foam, and consequently the transient transonic regime dynamics. |
| Databáze: | OpenAIRE |
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