Atlas Line-Imaging ORVIS Diagnostic

Many pulsed-power facilities used for high energy density experiments require diagnostics that can measure the velocity histories of shocked materials. The Atlas pulsed-power Z-pinch machine (located at the Nevada Test Site) is a 23-megajoule capacitor bank capable of delivering 28 mega-amperes in an approximately 5 microsecond rise time pulse into a cylindrical imploding liner. Experimental data are needed for the hydro-modeling of dynamic friction. For this set of experiments, shocks in two adjacent materials will produce differential shear velocities. An optically recording velocity interferometer system (ORVIS) has been designed to measure the differential velocity from the inner surface of a load after shock breakout. The moving target surface located inside an imploding load is illuminated with an f/10 laser pulse at 532 nm, focused down to a 12-mm long line. An optical relay collects light from the middle 8-mm of this line at f/15. Relay lenses pass collimated light through a two-arm interferometer, in the same fashion as VISAR (velocity interferometer system for any reflector). Different thicknesses of e acutetalons in one arm allow recording of different velocity ranges. After the interferometer, a dove prism rotates the line image into the slit of the recording streak camera. Alignment techniques are discussed and test calibration data from laser-driven mini-flyer plates are presented.