Characterization of similar Marshak waves observed at the LMJ
Abstract
We detail results of two experiments performed at the Laser Mégajoule (LMJ) facility aimed at
studying similar supersonic Marshak waves propagating in a low-density SiO2 aerogel enclosed
in metallic tubes. Similar means here that these two experiments, driven by the same input
radiation temperature history, use purposely very different tubes in term of length (L = 1200
μm or 2000 μm), diameter (2R = 1000 μm or 2000 μm), nature of the wall (gold or copper) and
aerogel densities ( = 30 mg/cm3 or 20 mg/cm3), yet the transit time and the radiation
temperature of the fronts at the tube exit are the same for both shots. Marshak waves are
characterized at the exit using simultaneously for the first time to our knowledge, a one
dimensional soft x-ray imager from which the radiation front transit time and curvature are
measured and also a broadband x-ray spectrometer to infer its temperature history. These
constraining results are then successfully compared to those from simple analytical models
[A.P. Cohen et al., Phys. Rev. Research 2, 023007 (2020) and O. A. Hurricane et al., Phys.
Plasmas 13, 113303 (2006)] and from the three dimensional Lagrangian radiationhydrodynamics
code TROLL to get information on x-ray energy losses. Controlled
compensation effects between the length, diameter and nature of the tubes (governing these
losses) are such that the radiation temperature drop along the tubes is eventually the same for
these two similar shots.
Domains
Physics [physics]| Origin | Publisher files allowed on an open archive |
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