Numerical study of the ablative Richtmyer-Meshkov instability of laser-irradiated deuterium and deuterium-tritium targets
- Dipartimento SBAI, Universita di Roma 'La Sapienza', Roma 00161 (Italy)
- Italy
The Richtmyer-Meshkov instability (RMI) at the ablation front of laser-irradiated planar targets is investigated by two-dimensional numerical hydrodynamics simulations. The linear evolution of perturbations seeded either by surface roughness or target inhomogeneity is studied for perturbation wavelengths in the range 10{<=}{lambda}{<=}400 {mu}m and laser intensity 4x10{sup 12{<=}}I{<=}4x10{sup 14} W/cm{sup 2} (with laser wavelength {lambda}{sub laser}=0.35 {mu}m). Thin and thick cryogenic deuterium or deuterium-tritium (DT) planar targets are considered. For targets irradiated at constant intensity, it is found that perturbations with wavelength below a given threshold perform damped oscillations, while perturbations above such a threshold are unstable and oscillate with growing amplitude. This is qualitatively in agreement with theoretical predictions by Goncharov et al. [Phys. Plasmas 13, 012702 (2006)], according to which ablation related processes stabilize perturbations with kD{sub c}>>1, where D{sub c} is the distance between the ablation front and critical density for laser propagation. For kD{sub c}<1 a weakly growing Landau-Darrieus instability (LDI) is instead excited. The stability threshold increases substantially with laser intensity, given the dependence of D{sub c} on laser intensity I (roughly D{sub c{proportional_to}}I, according to the present simulations). Direct-drive laser fusion targets are irradiated by time-shaped pulses, with a low intensity initial foot. In this case, perturbations with wavelengths below some threshold (about 10 {mu}m, for typical ignition-class all-DT targets) are damped after an initial growth. In a thin target, initial perturbations, either damped or amplified by RMI and LDI, seed the subsequent Rayleigh-Taylor instability. Finally, it is shown that RMI growth of fusion targets can be reduced by using laser pulses including an initial adiabat-shaping picket (originally proposed to reduce the growth of Rayleigh-Taylor instability).
- OSTI ID:
- 21531993
- Journal Information:
- Physics of Plasmas, Vol. 17, Issue 11; Other Information: DOI: 10.1063/1.3505112; (c) 2010 American Institute of Physics; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Single-mode, Rayleigh-Taylor growth-rate measurements on the OMEGA laser system
Early stage of implosion in inertial confinement fusion: Shock timing and perturbation evolution
Related Subjects
ABLATION
DEUTERIUM
LASERS
NUMERICAL ANALYSIS
PLASMA SIMULATION
RAYLEIGH-TAYLOR INSTABILITY
ROUGHNESS
SURFACES
TRITIUM TARGET
TWO-DIMENSIONAL CALCULATIONS
HYDROGEN ISOTOPES
INSTABILITY
ISOTOPES
LIGHT NUCLEI
MATHEMATICS
NUCLEI
ODD-ODD NUCLEI
SIMULATION
STABLE ISOTOPES
SURFACE PROPERTIES
TARGETS