A VISAR Velocity Interferometer System at MRL for Slapper Detonator and Shockwave Studies
MATERIALS RESEARCH LABS ASCOT VALE (AUSTRALIA)
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This report describes the commissioning and appraisal of a conventional 3-detector VISAR velocity interferometer system Systems, Science, and Software, Model 3SLVI-401 for measuring the velocity-time histories of small plastic flyer plates produced by exploding bridge foil generators. Proper treatment of the flyer surface to diffusely reflect the laser beam was found to be important. Roughening the surface with a miniature grit-blaster produced the best results. Peak velocities in the range 1500 ms to 3900 ms were obtained for small- and medium-scale flyers bridge widths of 0.25 mm and 1.5 mm, respectively. Accelerations were in the range 10 Gms2 to 100 Gms2. The uncertainty of the measurements was found to be related to the limited high- frequency response less than 100 MHz of the photodetectors. After replacement of the original non-flat beamsplitter, the arms of the interferometer were not quite compensated. A modified VISAR velocity equation that allows for the effective etalon length of the lambda8 waveplatebeamsplitter combination is derived.