X-ray imaging diagnostics for the inertial confinement fusion experiments (abstract)

Abstract

We report on our continued development of the advanced x-ray plasma diagnostics based on spherically curved crystals. The diagnostics include x-ray spectroscopy with one-dimensional (1D) spatial resolution, 2D monochromatic self-imaging, and backlighting, and can be extended to the x-ray collimating and 2D absorption and emission spectroscopy. The system is currently used, but not limited to diagnostics of the targets ablatively accelerated by the NRL Nike KrF laser. A spherically curved quartz crystal (2d=6.687 03 Å, R=200 mm) has been used to produce monochromatic backlit images with the He-like Si resonance line (1865 eV) as the source of radiation. The spatial resolution of the x-ray optical system is 1.7 μm in selected places and 2–3 μm over a larger area. Another quartz crystal (2d=8.5099 Å, R=200 mm) with the H-like Mg resonance line (1473 eV) has been used for backit imaging with higher contrast. Sherically curved mica (2d=9.969 Å in the second order or reflection, R=200 mm) has been used for backlighting of the low density foam cryotargets with the backlighter energy of 1.26 keV. Time resolution is obtained with the help of a four-strip x-ray framing camera. Time resolved, 20×magnified, backlit monochromatic images of CH planar targets driven by the Nike facility have been obtained with spatial resolution of 2.5 μm in selected places and 5 μm over the focal spot of the Nike laser. A second crystal with a separate backlighter has been added to the imaging system. This makes it possible to use all four strips of the framing camera. As a result we have four monochromatic snapshots of developing instabilities. We are currently exploring the enhancement of this technique to the higher and lower x-ray energies. A progress in high energy (4.5 keV) backlighting that has been made in cooperation with the LLNL will be reported.

Diagnostics development plan for ZR.

“…Use of state-of-the art MCP geometry (2 µm pore size, 3 µm center-to-center pore spacing) would provide acceptable spatial resolution. The limitations on spatial resolution in point-projection backlighting of 25-50 µm imposed by the size of the laser beam spot and expanding plasma plume on the x-ray source foil may be overcome by using a variety of x-ray optic and microscopy techniques [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Near-normal crystal microscopy systems have been shown to be more efficient than pinhole camera imaging systems with the same spatial resolution and magnification [14,16].…”