Detailed diagnosis of a double-shell collision under realistic implosion conditions

Abstract

Double-shell implosions provide a noncryogenic path to inertial confinement fusion. In the double-shell target, the energy is absorbed in an outer shell that is accelerated inward and collides with an inner shell that implodes against the deuterium fuel. Symmetric collision of the shells requires that the shells be illuminated and built symmetrically. In reality, the targets are complicated and the construction is not symmetric, due to the seam that our current assembly method requires. Using the Omega laser [R. T. Boehly, Opt. Comm. 133, 495 (1997)], an illumination strategy was designed that uses 40 beams in an offset geometry, leaving 20 beams to perform radiography from two different directions. This places a significant nonsymmetric illumination challenge that may not exist in final targets shot on the National Ignition Facility. This paper presents a measurement of the time history of a collision of two shells in a double-shell capsule, briefly reviews the illumination geometry, gives the results of the measurements of the trajectory and symmetry of the outer and inner shells, shows the effect of a seam on the inner shell implosion, and compares the results with calculations. The measurement of such a collision in a spherical geometry is of great interest to the study of double-shell implosions as well as code validation. © 2006 American Institute of Physics.