Mix and hydrodynamic instabilities on NIF

Abstract

A: Several new platforms have been developed to experimentally measure hydrodynamic instabilities in all phases of indirect-drive, inertial confinement fusion implosions on National Ignition Facility. At the ablation front, instability growth of pre-imposed modulations was measured with a face-on, x-ray radiography platform in the linear regime using the Hydrodynamic Growth Radiography (HGR) platform. Modulation growth of "native roughness" modulations and engineering features (fill tubes and capsule support membranes) were measured in conditions relevant to layered DT implosions. A new experimental platform was developed to measure instability growth at the ablator-ice interface. In the deceleration phase of implosions, several experimental platforms 1Corresponding author.

Rayleigh–Taylor instabilities in high-energy density settings on the National Ignition Facility

“…A wide variety of experiments are being performed on the NIF to study the hydrodynamics of ICF capsule implosions (17, 35–45). At the ablation front, instability growth of preimposed modulations was measured with in-flight, time-resolved, face-on, X-ray radiography (35, 36, 39, 46, 47).…”

“…At the ablation front, instability growth of preimposed modulations was measured with in-flight, time-resolved, face-on, X-ray radiography (35, 36, 39, 46, 47). Perturbation growth of “native roughness” modulations and engineering features such as fill tubes and capsule support membranes was also measured (37, 42, 48), as was instability growth at the ablator–ice interface (41). In the deceleration phase of implosions, RT growth from low-mode asymmetries and high-mode perturbations was measured near peak compression with X-ray and nuclear techniques.…”

“…Results from mix experiments and simulations on the NIF (17, 37). ( A ) The experimental configuration for an inflight radiography capsule implosion experiment on the NIF, showing the capsule, the hohlraum radiation cavity, the face-on backlighter, and a subset of the lasers used.…”

“…This equation is only approximate, but does illustrate that the RT growth rate, γ RT , decreases as va and L increase. Defining the classical RT growth rate as classical γclassical=(Akg)1/2, it is generally the case that ablation-front RT growth is reduced from classical, γRT<γclassical, an effect which is typically referred to as “ablative stabilization.” There is an ongoing effort at the NIF to understand and control ablation-front RT growth and hot-spot mix, for the various drive pulse shapes (laser power vs. time) that are used in ICF and HED research (13, 17, 34–37). Typical pressures at the ablation front on the NIF can range from ∼1 TPa to 10 TPa or higher.…”

Progress on Understanding Rayleigh–Taylor Flow and Mixing Using Synergy Between Simulation, Modeling, and Experiment

“…RT mixing is central to the deflagration-to-detonation transition of thermonuclear flames in type Ia supernovae [12][13][14]. RT instability and mixing in inertial confinement fusion [15,16] capsules decreases the efficiency of thermonuclear burning [17][18][19] and is one of the mechanisms preventing gain and ignition of thermonuclear fuel in the laboratory [20]. In geophysics, RT instability exists in the lithosphere [21][22][23].…”