Effect of preheating on the nonlinear evolution of the ablative Rayleigh-Taylor instability

Abstract

The evolution of the ablative Rayleigh-Taylor instability (ARTI) in the presence of preheating is investigated. When the linear ARTI growth rate has a sharp maximum, a secondary spike-bubble structure at a harmonic of the fundamental mode will be excited. Interaction of this secondary structure with the latter will eventually lead to its rupture. On the other hand, for stronger preheating the linear growth rate has no sharp maximum and in the nonlinear evolution no secondary spike-bubble is generated. Instead, the fundamental spike-bubble structure evolves into an elongated jet. These results are in agreement with that from the numerical simulations and observations.

Numerical investigation on the stabilization of the deceleration phase Rayleigh-Taylor instability due to alpha particle heating in ignition target

“…Numerical simulation result by Atzeni et al [11] confirms the validity of ablative stabilization of dp-RTI. Garnier and Cherfils obtained a analytical formula for dp-RTI [12], whose result generally agrees with that of Lobatchev in most of the existing works, the energy deposition of the alpha particles is treated as energy source into the electrons, actually the nonlocal energy transport of the alpha particles can directly heat the main fusion fuel and greatly enhance the mass ablation at the hot spot boundary (inner ablation front), which acts like preheating [14] and has strong stabilizing effect on dp-RTI. When the nuclear reaction gets strong enough, its stabilization effect becomes much stronger than that of the electron conduction.…”

Numerical investigation on the ablative Kelvin-Helmholtz instability

“…In the ablative nonlinear Rayleigh-Taylor (RT) [7] and Richtmyer-Meshkov (RM) [8] instabilities in inertial confinement fusion (ICF), the jet-like long spike is observed [9][10][11]. Shear flows are formatted significantly at (a) E-mail: ye wenhua@iapcm.ac.cn both sides of the spike, especially at the tips (mushroom head).…”

“…The shear flows are also formed when the shocks pass through the irregular interfaces [12]. The main reason for the formation of the long jet-like spike is assumed that the ablative effect weakens the KH instability growth [9].…”

“…-In 1D calculations, we choose the pressure generated by the typical laser in ICF experiments or radiative shock wave in modeling astrophysical phenomena in the laboratory [9][10][11][12][13]. The initial density profiles are from the typical pellet implosion calculations in ICF [9,10,17]. We analyze three typical initial density profiles.…”

Indirect-drive ablative Rayleigh-Taylor growth experiments on the Shenguang-II laser facility

“…During the acceleration phase of the ICF implosion, small perturbations in the shell's areal density ðqRÞ seeded by manufacturing defects and/or laser non-uniformities which have undergone the RM growth grow at the ablation-front and ablator-fuel interface due to the RT instability (RTI) and Bell-Plesset (BP) Effects. [8][9][10] As the target shell converts its kinetic energy into hotspot internal energy (i.e., the deceleration phase), the qR perturbations at the shell's inner surface grow due to RTI, RMI, and BP effects, forming the jet-like cold spikes, 11,12 which would hinder the hotspot formation and shrink the size of the hotspot. Additionally, the material mixing from the ablator to the hotspot due to ablation-front instability has been identical as the main factor leading to the performance degrading of the implosion.…”