(a) and (b) Schematic illustrations of the two-frame monochromatic radiography diagnostic. (c) Half-section illustration of the load region for a typical Be liner experiment on the Z accelerator. (d) Drive current and radiograph times (vertical lines) from each experiment and reference implosion trajectories for the liner's inner and outer surfaces from a 1D simulation.
(a) Radiographs with the full 0%–100% transmission range displayed. (b) Same as (a) with only 0%–30% transmission displayed in order to enhance the contrast and visibility of the liner's inner surface (i.e., the inner aluminum sleeve). (c) Reconstructed mass density images obtained by Abel inverting the corresponding radiographs shown in (a). The latest image (the bottom row) was taken while the liner was stagnating on the 200-μm-diameter tungsten wire. The vertical dashed lines indicate the initial positions of the liner's inner and outer surfaces.
Radiograph illustrating the effect of the “wall instability.” This radiograph is from an experiment where the radiography diagnostic was aligned high and imaged the early implosion of an MRT bubble near the upper (anode) electrode surface. The liner was again an AR = 6 Be tube with a 2-μm-thick inner Al sleeve. The dashed vertical lines represent the initial positions of the liner's inner and outer surfaces.
Comparisons between shock and shockless (quasi-isentropic) liner compression. All of the liners were AR = 4 Be liners with initial inner and outer radii of 2.39 and 3.19 mm, respectively. (a) Example radiographic image of a shockwave propagating through the liner wall with the full 0%–100% transmission range displayed. (b) Same as (a) with only 0%–30% transmission displayed in order to enhance the contrast of the shock front within the liner wall. (c) Reconstructed mass density image obtained by Abel inverting the radiograph shown in (a). (d) Example radiographic image of a liner undergoing shockless (quasi-isentropic) compression and with the full 0%–100% transmission range displayed. (e) Same as (d) with only 0%–30% transmission displayed. (f) Reconstructed mass density image obtained by Abel inverting the radiograph shown in (d). (g) Two representative load current pulses on the Z accelerator. The standard short pulse (red) was used to drive the shock compression experiments while the shaped pulse (blue) was used to drive the shockless compression experiments. (h) Radial mass density profiles from shock compression experiments. Also plotted are two radial mass density profiles from a 1D ALEGRA simulation. The two simulation times plotted correspond to the earliest and latest experiment times. (i) Radial mass density profiles from shockless compression experiments. The shockless compression data presented here are the same data that were presented in Refs. 18 and 19 .
(a) Photograph of the micro- probes and the Be liner assembled in their custom anode fixture. (b) Computer rendering of micro- probes installed in the experiment hardware. (c) Half-section cutaway view of that shown in (b). (d) Photograph of micro- probes, liner load, and other diagnostics (e.g., the monochromatic crystal backlighter for radiography, load-current probes, etc.) installed in the Z accelerator vacuum chamber just prior to the experiment. Shielded 0.086″ diameter coaxial cables relayed the signals from the SMA connectors of the micro- probes to the feedthrough ports of the Z accelerator's vacuum chamber.
measurement results from a differential pair of 0.020″ micro- probes and from a differential pair of 0.047″ micro- probes, as well as synthetic results from 1D ALEGRA and 1D GORGON simulations. The large blue and green circles indicate the likely failure points of the individual micro- probes that make up the 0.020″ and 0.047″ differential pairs, respectively (there are two blue circles indicating that the individual probes of the 0.020″ pair likely failed at different times). The error bars show the spread in the measurements from the individual probes (i.e., the “single-ended” measurements, where the common-mode noise has not been reduced). Also plotted are the measured load current and radiograph times from this experiment (z2318), as well as reference implosion trajectories for the liner's inner and outer surfaces from a 1D ALEGRA simulation. This figure illustrates that penetration commences shortly after the shockwave (see Sec. III ) breaks out from the liner's inner surface.
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