Atlas Axial Radiography

Abstract

The Atlas pulsed-power machine [1] is a 23-megajoule capacitor bank that delivers 28 mega-amperes in a 5 microsecond rise-time pulse into a cylindrical imploding liner, which often contains a target. It is used to study the hydrodynamic behavior of various materials under well- controlled high-energy conditions. X-ray imaging or radiography is used to infer trajectories and velocities of the Shockwave and the material interfaces in the target. The axial radiography diagnostic records four high-speed flash x-ray snapshots through the target axis during an experiment. These images provide important benchmarks for various hydrodynamic codes currently used to predict the behavior of shocked materials. Four Marx-driven x-ray diode sources [2], designed by Los Alamos National Laboratory (LANL) and fabricated by Bechtel Nevada, are used. Each source has a pulse duration of 20 nanoseconds full-width half-maximum (FWHM) that thereby freezes the motion of the target [3]. The x-ray images are converted into blue visible light by a scintillator. Two 8-inch-diameter doublet lenses relay this image 6 meters away into a microchannel plate image- intensified framing camera, contained in a screen box. The machine energy destroys the scintillator and sometimes the first relay doublet. The optical relay is realigned for each experiment. Calibration images are stored for each shot. The image data are sent over fiberoptic cables for remote recording.