Application of Microgravity and Containerless Environments to the Investigation of Fusion Target Fabrication Technology
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APPLICATION OF MICROGRAVITY AND CONTAINERLESS ENVIRONMENTS TO THE INVESTIGATION OF FUSION TARGET FABRICATION TECHNOLOGY*
MARK C. LEE, JAMES M. KENDALL, DANIEL D. ELLEMAN, WON-KYU RHIM, ROGER S. HELIZON, CHARLES L. YOUNGBERG, I-AN FENG AND TAYLOR G. WANG
let Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 ABSTRACT During the past few years we have been studying several of the physical processes relevant to the production of spherical shells for inertial confinement fusion targets, both in a microgravity environment and in a containerless environment. The work has led to the development of several experimental facilities. Those which are most unique are described here, and fall into three categories as follows: 1. Ones which provide an induced low- or microgravity containerless environment, such as a vertical drag-free wind tunnel, two differing low-pressure and/or high-temperature drop towers for processing metallic or metallic-glass specimens, and a neutral buoyancy tank, 2. Ones providing containerless processing capability, such as a focusing Ones radiator and an electrostatic levitator and 3. providing extended microgravity and containerless capabilities, such as the KC-135 aircraft and the Space The physical processes Processing Application Rockets. which we have been studying include, but are not limited to, those which establish the shell sphericity, concentricity, surface topology, material properties, coatings, heating and cooling requirements and the effects of gravity on fusion pellet fabrication processes. INTRODUCTION Current technologies for the fabrication of high-quality inertial the pellet confinement fusion targets must deal with three parameters: dimensions, pellet sphericity and concentricity, and the surface topology of the pellet. At present, KMS Fusion, Inc., and, in particular, Lawrence Livermore National Laboratory have successfully controlled these parameters for glass pellets [1,2,3]. Various aspects of these technologies are, however, difficult to generalize to cover other pellet materials, such as high-Z metals and It is, therefore, important to develop alternative metallic glasses. technologies which would circumvent or overcome problems of scale-up and of material processing. The objective of our work has been to explore certain areas to be described, with emphasis upon understanding the underlying physical parameters concerning materials and their mechanical and fluid-dynamic behavior. A highly simplified version of a multilayer ablative-type fusion target is depicted in Figure 1. In this configuration, a glass micrtballoon charged with high pressure DT fuel is coated with layers of high-Z metal, polymer, and low-Z *This research carried out by the let Propulsion Laboratory, California Institute of Technology, under contract with NASA.
96 metal. Physical parameters critical to the fabrication of this type of target involve the permeability of the shell to the DT fuel, the sphericity concentricity, and the surface finish of each layer. Aside from o
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