Classical and ablative Richtmyer–Meshkov instability and other ICF-relevant plasma flows diagnosed with monochromatic x-ray imaging

Abstract

Abstract. In inertial confinement fusion (ICF) and high-energy density physics (HEDP), the most important manifestations of the hydrodynamic instabilities and other mixing processes involve lateral motion of the accelerated plasmas. In order to understand the experimental observations and to advance the numerical simulation codes to the point of predictive capability, it is critically important to accurately diagnose the motion of the dense plasma mass. The most advanced diagnostic technique recently developed for this purpose is the monochromatic x-ray imaging that combines large field of view with high contrast, high spatial resolution and large throughput, ensuring high temporal resolution at large magnification. Its application made it possible for the experimentalists to observe for the first time important hydrodynamic effects that trigger compressible turbulent mixing in laser targets, such as ablative Richtmyer-Meshkov (RM) instability, feedout, interaction of a RMunstable interface with rarefaction waves. It also helped to substantially improve the accuracy of diagnosing many other important plasma flows, ranging from laser-produced jets to electromagnetically driven wires in a Z-pinch, and to test various methods suggested for mitigation of the Rayleigh-Taylor instability. We will review the results obtained with the aid of this technique in ICF-HEDP studies at the Naval Research Laboratory and the prospects of its future applications.

Transverse coupling property of beam from ECR ion sources

“…A modification of the traditional x-ray monochromatic backlighting scheme is the x-ray crystal imaging microscope (XCIM), [6][7][8][9][10] where the Bragg angles can deviate substantially a) Contributed paper, published as part of the Proceedings of the 20th Topical Conference on High-Temperature Plasma Diagnostics, Atlanta, Georgia, USA, June 2014. b) Author to whom correspondence should be addressed. Electronic mail:…”

Implosion dynamics measurements by monochromatic x-ray radiography in inertial confinement fusion

“…So the convergent ablator performances can be inferred with more accurately. This high spatial resolution diagnostics with high magnification will also be helpful to observe the RayleighTaylor bubble and spike features from backlit radiographs 15,24,25 in future. …”

“…The spectral resolution is not larger than 1 Â 10 À3 k in our configuration. A contrast aperture of 2 mm in diameter in the reflected beam is used to protect the detector from a significant portion of the self-radiation 14,15 as shown in Fig. 1.…”

“…The variations will be seen inevitably in the image obtained since different points of a sample are backlit by different parts of a backlighter. 14,15 Unfortunately, the variations are difficult to be measured independently. The spectral purity of the backlighter and the resolution of the detector system are also hardly improved.…”

Monochromatic radiography of high energy density physics experiments on the MAGPIE generator

“…Monochromatic backlighters, based on Bragg reflection near normal incidence from a spherically bent crystal, 2, 3 have previously been used to image wire-array Z-pinches and pulsed-power-driven HEDP experiments 4 and laser-plasma interactions relevant to Inertial Confinement Fusion. 5,6 A monochromatic backlighter has been developed for the study of HEDP experiments on MAGPIE, 1 a pulsed power generator capable of producing a 1.4 MA electrical pulse with a rise time of 240 ns. This instrument uses a spherically bent quartz 1011 crystal to perform radiography with 1.865 keV X-rays (Silicon He-α) driven by a ≈7 J, ≈1 ns, 527 nm pulse from a long-pulse arm of the Cerberus multibeam laser system.…”