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Comparison of longitudinal and transverse smoothing by spectral dispersion on stimulated Brillouin backscattering in inertial confinement fusion plasmas
- Source :
- Physics of Plasmas. 26:042707
- Publication Year :
- 2019
- Publisher :
- AIP Publishing, 2019.
-
Abstract
- In the context of inertial confinement fusion, optical smoothing is a technique used to provide laser irradiation as homogeneous as possible. It is required for limiting the development of laser-plasma instabilities, in particular, stimulated Brillouin backscattering (SBS). Here, we carefully compare longitudinal and transverse smoothing by spectral dispersion in an ideal smoothing configuration for each case. With 3D codes, we have simulated SBS in a gold plasma. We show that, as opposed to common belief, the time evolution of the SBS reflectivity exhibits some differences between both smoothing schemes. First, the asymptotic values of the saturation levels are not quite the same. With a simple ray description and computing the SBS gain for each ray, we were able to explain this difference. Moreover, the dynamics of SBS are also somewhat different. We have shown that SBS dynamics are driven by the time evolution of speckle properties and in particular by the effective interaction length between the Brillouin backscattered light and the hot-spots. This effective interaction length depends both on the longitudinal velocity and on the length of the hot-spots. As a matter of fact, synchronizing the effective interaction lengths of both smoothing schemes also synchronizes the backscattering curves before reaching the saturation level.
- Subjects :
- Physics
Time evolution
Physics::Optics
Plasma
Condensed Matter Physics
Laser
01 natural sciences
010305 fluids & plasmas
law.invention
Computational physics
Brillouin zone
Speckle pattern
Transverse plane
Physics::Plasma Physics
law
0103 physical sciences
010306 general physics
Inertial confinement fusion
Smoothing
Subjects
Details
- ISSN :
- 10897674 and 1070664X
- Volume :
- 26
- Database :
- OpenAIRE
- Journal :
- Physics of Plasmas
- Accession number :
- edsair.doi...........f6a7e858e4044b122182110b31fa185a
- Full Text :
- https://doi.org/10.1063/1.5089113