Real and complex valued geometrical optics inverse raytracing for inline field calculations
In this work, a 3D ray based model for computing laser fields in dissipative and amplifying media is presented. The eikonal equation is solved using inverse raytracing on a dedicated nonstructured 3D mesh. Inverse raytracing opens the possibility of using Complex Geometrical Optics (CGO), for which we propose a propagation formalism in a finite element mesh. Divergent fields at caustics are corrected using an etalon integral method for foldtype caustics. This method is successfully applied in dissipative media by modifying the rayordering and root selection rules, thereby allowing one to reconstruct the field in the entire caustic region. In addition, we demonstrate how caustics in the CGO framework can disappear entirely for sufficiently dissipative media, making the complex ray approach valid in the entire medium. CGO is shown to offer a more precise modeling of laser refraction and absorption in a dissipative medium when compared to Geometrical Optics (GO). In the framework of Inertial Confinement Fusion (ICF), this occurs mostly at intermediate temperatures or at high temperatures close to the critical density. Additionally, GO is invalid at low temperatures if an approximated expression of the permittivity is used. The inverse raytracing algorithm for GO and CGO is implemented in themore »
 Authors:

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 Univ. of Rochester, NY (United States). Lab. for Laser Energetics
 Publication Date:
 Report Number(s):
 2018307; 1481
Journal ID: ISSN 1070664X; 2018308, 1481, 2440
 Grant/Contract Number:
 NA0003856
 Type:
 Accepted Manuscript
 Journal Name:
 Physics of Plasmas
 Additional Journal Information:
 Journal Volume: 26; Journal Issue: 3; Journal ID: ISSN 1070664X
 Publisher:
 American Institute of Physics (AIP)
 Research Org:
 Univ. of Rochester, NY (United States). Lab. for Laser Energetics
 Sponsoring Org:
 USDOE National Nuclear Security Administration (NNSA)
 Contributing Orgs:
 Univ. of Rochester, NY (United States). Lab. for Laser Energetics
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
 OSTI Identifier:
 1505766
Colaïtis, A., Palastro, J. P., Follett, R. K., Igumenschev, I. V., and Goncharov, V.. Real and complex valued geometrical optics inverse raytracing for inline field calculations. United States: N. p.,
Web. doi:10.1063/1.5082951.
Colaïtis, A., Palastro, J. P., Follett, R. K., Igumenschev, I. V., & Goncharov, V.. Real and complex valued geometrical optics inverse raytracing for inline field calculations. United States. doi:10.1063/1.5082951.
Colaïtis, A., Palastro, J. P., Follett, R. K., Igumenschev, I. V., and Goncharov, V.. 2019.
"Real and complex valued geometrical optics inverse raytracing for inline field calculations". United States.
doi:10.1063/1.5082951.
@article{osti_1505766,
title = {Real and complex valued geometrical optics inverse raytracing for inline field calculations},
author = {Colaïtis, A. and Palastro, J. P. and Follett, R. K. and Igumenschev, I. V. and Goncharov, V.},
abstractNote = {In this work, a 3D ray based model for computing laser fields in dissipative and amplifying media is presented. The eikonal equation is solved using inverse raytracing on a dedicated nonstructured 3D mesh. Inverse raytracing opens the possibility of using Complex Geometrical Optics (CGO), for which we propose a propagation formalism in a finite element mesh. Divergent fields at caustics are corrected using an etalon integral method for foldtype caustics. This method is successfully applied in dissipative media by modifying the rayordering and root selection rules, thereby allowing one to reconstruct the field in the entire caustic region. In addition, we demonstrate how caustics in the CGO framework can disappear entirely for sufficiently dissipative media, making the complex ray approach valid in the entire medium. CGO is shown to offer a more precise modeling of laser refraction and absorption in a dissipative medium when compared to Geometrical Optics (GO). In the framework of Inertial Confinement Fusion (ICF), this occurs mostly at intermediate temperatures or at high temperatures close to the critical density. Additionally, GO is invalid at low temperatures if an approximated expression of the permittivity is used. The inverse raytracing algorithm for GO and CGO is implemented in the IFRIIT code, in the framework of a dielectric permittivity described in 3D using a piecewise linear approximation in tetrahedrons. Fields computed using GO and CGO are compared to results from the electromagnetic wave solver LPSE. Excellent agreement is obtained in 1D linear and nonlinear permittivity profiles. Good agreement is also obtained for ICFlike Gaussian density profiles in 2D. Finally, we demonstrate how the model reproduces Gaussian beam diffraction using CGO. The IFRIIT code will be interfaced inline to 3D radiative hydrodynamic codes to describe the nonlinear laser plasma interaction in ICF and highenergydensity plasmas.},
doi = {10.1063/1.5082951},
journal = {Physics of Plasmas},
number = 3,
volume = 26,
place = {United States},
year = {2019},
month = {3}
}
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