Using Refracted Enhanced Radiograph (RER) to study of the ice-ablator interface in ICF capsule implosion at the National Ignition Facility *

Streaked X-ray Refraction Enhanced Radiography (RER)¹ experiments give a direct measurement of density gradients at both fuel ice/ablator interface and ablation front in indirect drive capsule implosions at the National Ignition Facility. They will provide insight into the observed reduced compression in recent ICF implosions². We focused our efforts on two different phases: the N+1 shock phase and the early time acceleration of the ice-ablator interface.

 

The N+1 shock occurs when the rarefaction wave goes back to the interface after being reflected. While a previous streaked RER of an ICF implosion showed reduced fuel compression during this phase compared to prediction¹, a recent experiment was conducted with improvements that increased the data quality during this phase. Furthermore, being able to control the ice/abator interface stability is also crucial as it will affect the compression as well. Thus, we are conducting a series of experiments on early time measurement of RER to track the trajectory of the ice-ablator interface that will allow the observation of a potential acceleration phase with a given set of drive parameters. We will compare the RER results with hydrodynamic simulations.

 

[1] E.L. Dewald, O.L. Landen, et al, High En. Dens. Phys. 36, 100795 (2020).

[2] D.S. Clark, S.W. Weber, et al, Phys. Plasmas 26, 050601 (2019).