Ph. Nicolaï

A nonlocal electron conduction model for multidimensional radiation hydrodynamics codes

Numerical simulation of laser driven Inertial Confinement Fusion (ICF) related experiments require the use of large multidimensional hydro codes. Though these codes include detailed physics for numerous phenomena, they deal poorly with electron conduction, which is the leading energy transport mechanism of these systems. Electron heat flow is known, since the work of Luciani, Mora, and Virmont (LMV) [Phys. Rev. Lett. 51, 1664 (1983)], to be a nonlocal process, which the local Spitzer–Harm theory, even flux limited, is unable to account for. The present work aims at extending the original formula of LMV to two or three dimensions of space. This multidimensional extension leads to an equivalent transport equation suitable for easy implementation in a two-dimensional radiation-hydrodynamic code. Simulations are presented and compared to Fokker–Planck simulations in one and two dimensions of space.

Fast ignitor target studies for the HiPER project

Target studies for the proposed High Power Laser Energy Research (HiPER) facility [M. Dunne, Nature Phys. 2, 2 (2006)] are outlined and discussed. HiPER will deliver a 3ω (wavelength λ=0.35μm), multibeam, multi-ns pulse of about 250kJ and a 2ω or 3ω pulse of 70–100kJ in about 15ps. Its goal is the demonstration of laser driven inertial fusion via fast ignition. The baseline target concept is a direct-drive single shell capsule, ignited by hot electrons generated by a conically guided ultraintense laser beam. The paper first discusses ignition and compression requirements, and presents gain curves, based on an integrated model including ablative drive, compression, ignition and burn, and taking the coupling efficiency ηig of the igniting beam as a parameter. It turns out that ignition and moderate gain (up to 100) can be achieved, provided that adiabat shaping is used in the compression, and the efficiency ηig exceeds 20%. Using a standard ponderomotive scaling for the hot electron temperature, a 2ω or 3ω ...

Fast-electron transport and induced heating in aluminum foils

Beams of fast electrons have been generated from the ultra-intense laser interaction (6×1019W cm−2, 40fs) with aluminum foil targets. The dynamics of fast-electron propagation as well as the level of induced in-depth heating have been investigated using the optical emission from the foil’s rear side. The dependence of the emitted signals spectrum and size on the target thickness allowed the identification of the coherent (coherent transition radiation) and incoherent (thermal radiation) mechanisms of the optical emission. We demonstrate a two-temperature energy distribution for the laser-generated fast-electron population: a divergent bulk component (θbulk=35°±5°) with ≈35% of the laser focal spot energy and a 400–600keV temperature, plus a relativistic tail highly collimated (θtail=7°±3°), with a 10MeV temperature and a periodic modulation in microbunches, representing less than 1% of the laser energy. Important yields of thermal emission, observed for targets thinner than 50μm, are consequence of a hot ...

Laser-driven platform for generation and characterization of strong quasi-static magnetic fields

Quasi-static magnetic-fields up to

Generation of high pressure shocks relevant to the shock-ignition intensity regime

800\,

Compression phase study of the HiPER baseline target

T are generated in the interaction of intense laser pulses (

Plasma jets produced in a single laser beam interaction with a planar target

500\,

Comparison for non-local hydrodynamic thermal conduction models

J,

Studies on targets for inertial fusion ignition demonstration at the HiPER facility

1\,

A practical nonlocal model for heat transport in magnetized laser plasmas

ns,