Streaked radiography of an irradiated foam sample on the National Ignition Facility

Abstract

Streaked x-ray radiography images of annular patterns in an evolving tantalum oxide foam under the influence of a driven, subsonic radiation wave were obtained on the National Ignition Facility. This is the first successful radiography measurement of the evolution of well-defined foam features under a driven, subsonic wave in the diffusive regime. A continuous record of the evolution was recorded on an x-ray streak camera, using a slot-apertured point-projection backlighter with an 8 ns nickel source (7.9 keV). Radiography images were obtained for four different annular patterns, which were corrected using a source-dependent flat-field image. The evolution of the foam features was well-modeled using the 3D KULL radiation hydrodynamics code. This experimental and modeling platform can be modified for scaled high-energy-density laboratory astrophysics experiments.

Inertial confinement fusion: a defence context

“…These experiments (in collaboration with Los Alamos National Laboratory) also constrained several of the material properties required to model propagation of radiation through low-density foams and led to the development and qualification of new diagnostics on NIF. The ‘Searchlight' [20] campaign was aimed at validating radiation transport modelling using machined foam features driven by a laser-irradiated gold target to create a 200 eV X-ray source, which, in turn, irradiated a Ta 2 O 5 foam. Continuous images of the evolution of features in different foam patterns were captured on X-ray streak cameras.…”

Dynamic high energy density plasma environments at the National Ignition Facility for nuclear science research

“…Typical diagnostic suite Indirect drive implosions [26] 192 beams with a highcontrast shaped laser pulse designed to control the adiabat of the implosion Approx. 10 mm long and 6 mm diameter Au hohlraum target with a capsule at the center, may be cryogenically cooled X-ray imaging and bangtime measurements, neutron imaging, nuclear yield and spectrum Direct drive implosions [27] 192 beams with a shaped laser pulse designed to control the adiabat of the implosion 1-2 mm diameter freestanding capsule with gas-fill X-ray imaging and bangtime measurements, neutron imaging, nuclear yield and spectrum Shock timing and EOS [28,29] Varied configurations with up to 192 beams with square or shaped laser pulse -hohlraum with capsule, backlighter and diagnostic windows in horizontal plane of target -halfraum or directly driven package X-ray imaging with 2D gated or time-integrated static imager or 1D streaked imager Vertical axis radiography [32] Up to 96 beam with square or shaped laser pulse Halfraum or directly driven planar package X-ray imaging with 2D gated or time-integrated static imager or 1D streaked imager Vertical axis imaging [32] Varied configurations including 96-192 beams Varied targets, including halfraum, hohlraum, direct drive foil or capsule X-ray imaging with 2D gated or time-integrated static imager or 1D streaked imager X-ray conversion [33,34] Varied configurations: typically with 128-192 beams and square or shaped pulses Foam target, metal cylinder, gas pipe, or planar foil 2D gated x-ray imager with super-snout or 1D streaked x-ray imager with NIF x-ray spectrometer snout (NXS). Laser-plasma interactions [35] Varied configurations including single beams with square pulses up to 192 beams with ignition pulse shapes Gas-filled hohlraum or gas-tube target Optical backscatter, Dante x-ray drive, soft x-ray imaging engineering marvels in tiny packages.…”

Development of a Big Area BackLighter for high energy density experiments

“…However, the story is evolving, given the greater than expected conversion efficiencies measured on NIF. 22 For backlit radiography along the polar axis, point projection has been demonstrated to work quite well by Cooper et al 23 In this geometry, there is a lot of flexibility in setting the distances between the backlighter, detector, and target. This geometry also allows for a large number of beams on the backlighter with good pointing accuracy.…”