Review of hydrodynamic instability experiments in inertially confined fusion implosions on National Ignition Facility

Abstract

Hydrodynamic instabilities are a major factor in degradation of inertial confinement fusion (ICF) implosions. In the highest performing implosions on National Ignition Facility, yield amplification (YA) due to alpha particle heating approached ∼3, while YA of ∼15-30 is needed for ignition. Understanding and mitigation of the instabilities are critical to achieving ignition. This article reviews several experimental platforms that have been developed to directly measure these instabilities in all phases of ICF implosions. Measurements of ripple-shock propagation at OMEGA laser has provided results on initial seeds for the instabilities in three ablators-plastic (CH), beryllium, and high-density carbon. At the ablation front, instability growth of preimposed modulations was measured in the linear regime using the hydrodynamic growth radiography platform. This platform was extended for modulation growth of 'native roughness' modulations and engineering features (fill tubes and capsule support membranes or 'tents'). Several new experimental platforms have or are being developed to measure instability growth at the ablator-ice interface. In the deceleration phase of implosions, complementary 'self-emission' and 'self-backlighting' platforms were developed to measure low-mode asymmetries and highmode perturbations near peak compression.

One-dimensional hydrodynamic simulations of low convergence ratio direct-drive inertial confinement fusion implosions

“…However, this resulted in the onset of significant hydrodynamic instabilities, which meant that fusion performance was significantly worse than expected from the campaign based on simulations. These instabilities were a key reason the NIC was unsuccessful in achieving ignition (along with fill tube, tent and capsule imperfections, all of which are also exacerbated by high convergence ratio), and continue to be a major challenge in ICF experiments [ 4 ]. Further discussion of the significance of convergence ratio will follow in § 2 a.…”

The magnetised Richtmyer–Meshkov instability in two-fluid plasmas

“…The Richtmyer-Meshkov instability (RMI) (Richtmyer 1960;Meshkov 1969) of shock accelerated density interfaces plays a significant role in processes as varied as inertial confinement fusion (ICF) (Lindl et al 2014;Smalyuk et al 2019) and supernovae (Arnett 2000). In these physical phenomena, the materials involved are in the plasma state.…”

“…2014; Smalyuk et al. 2019) and supernovae (Arnett 2000). In these physical phenomena, the materials involved are in the plasma state.…”

Recent progress in quantifying hydrodynamics instabilities and turbulence in inertial confinement fusion and high-energy-density experiments

“…Considerable efforts were therefore devoted to the measurement and identification of mixing sources. For an extended review, please refer to [63]. Unexpected sources of perturbations such as capsule tents were discovered with the development of dedicated platforms [64][65][66].…”