Schematic of the probe laser injection into the 10 m long optical fiber. Two turning mirrors, M1 and M2, directed the beam into the fiber and a 250 mm focal length lens reduced the beam diameter to fit into the 2 mm diameter fiber. A flip mirror FM optionally directs a low power laser into the fiber for setup and alignment of the line-imaging VISAR diagnostic before the shot.
Experimental layout of the line-imaging VISAR near the target. Cylindrical lenses, CL1 and CL2, collimated the laser light from the output of the fiber before it was reflected from a turning mirror and a 50:50 beamsplitter. A turning mirror in the catch tank directed the light normal to the sample surface. An f/4 lens imaged the target. The return light transited the same path but passed through the beamsplitter and an image of the target was created and then relayed to the interferometer.
Schematic of the interferometer and detector. The target image is relayed from the gun room, and then it is collimated to pass through the interferometer. The image was subsequently reformed on the entrance slit of the streak camera, which was monitored with a CCD camera. For alignment and adjustment of the white light fringes, a flip mirror, FM, was used to direct light from a green LED into the interferometer with the use of a photographic lens assembly, PLA. An alignment telescope, AT, and a CCD camera were used to align the interferometer optics and to optimize the white light fringes before the etalons were inserted into the interferometer.
Schematic of the target configuration showing the configuration of the velocity diagnostics and the PZT triggering pin.
(a) Interferogram for symmetric sapphire impact of 10.42 GPa. (b) Interface velocity of sapphire data shown in (a) as a function of spatial position along the sample.
Power spectrum from the discrete Fourier transform of the interferogram shown in Fig. 5(a) . The dashed box shows the area which was selected for FFT analysis.
Particle velocity for symmetric sapphire experiment. The intensity plot shows the analyzed PDV data and the red line shows the average of the data from the line-imaging VISAR.
(a) Interferogram of partial reaction in DAAF after impact of 3.37 GPa and transit through 6.353 mm of DAAF. (b) Interface velocity from DAAF data shown in (a) as a function of spatial position along the sample.
(a) Interferogram of partial reaction in PBX 9501 after impact of 3.95 GPa and transit through 4.007 mm of PBX 9501. (b) Interface velocity from PBX9501 data shown in (a) as a function of spatial position along the sample.
Particle velocity for partial reaction in DAAF. The intensity plot shows the analyzed PDV data and the red line shows the average of data from the line-imaging VISAR.
Particle velocity for partial run to detonation in PBX 9501. The intensity plot shows the analyzed PDV data and the red line shows the average of the data from the line-imaging VISAR.
Power spectrum from the discrete Fourier transform of the PBX 9501 interferogram shown in Fig. 9(a) . The velocity heterogeneity is apparent in the additional frequencies that develop with increasing reaction.
Summary of experiment parameters.
Velocity heterogeneity starting 10 ns after arrival of the shock front and at the peak velocity. The velocity data was averaged for 10 ns at each of the times to obtain the spatial variation of the velocity.
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