The Development of the VISAR, and its Use in Shock Compression Science

VISAR predecessors are described, including the displacement and velocity interferometer techniques for shock instrumentation. The advance to the VISAR in 1972 made laser interferometry applicable to a very wide range of shockwave experiments. With a 1974 refinement of the VISAR data reduction equation, the VISAR was shown to produce velocity measurements with better than 1% accuracy, and with time resolution to about 2 ns. The power of the VISAR was demonstrated in a plate impact study of the 13 GPa phase transition in iron. Rate effects in shock compressed iron were measured and correlated with theory, and the unloading stress-volume path was determined, revealing the reverse phase transition stress to unprecedented accuracy. Later improvements in VISARs are reviewed, including the lens delay VISAR (Amery), the push-pull VISAR (Hemsing), the ORVIS (Bloomquist and Sheffield), the line VISAR (Hemsing), the fixed-cavity VISAR (Sweat, et al.), the “never-search-for-fringes” VISAR (Barker), and the multi-beam VISAR (Barker).