Preliminary Evaluation of Techniques to Fabricate Beryllium, Polyimide, and Ge-doped CH/CD Ablator Materials

Cook, B ; Letts, S ; Nikroo, A ; Nobile, A ; McElfresh, M ; Cooley, J ; Alexander, D

Lawrence Livermore National Laboratory

关键词: Evaluation;    Texture;    Plastics;    Absorption;    36 Materials Science;   

DOI  :  10.2172/15011415
RP-ID  :  UCRL-TR-208476
RP-ID  :  W-7405-ENG-48
RP-ID  :  15011415

美国|英语

来源: UNT Digital Library

【 摘 要 】

This report including appendices provides information to complete this deliverable. It summarizes the important features of each ablator material, with particular focus to its usefulness for ignition capsules. More detailed discussions of each ablator type are in the Appendix. Included at the end of each separate discussion in the Appendix is a list of all published work with an ICF focus on that ablator type. This report is organized into Be based and polymer (C) based ablators. We summarize status, outstanding issues, and how we plan to address them. Details are in the Appendix. For Be there are two fabrication routes, one by machining bulk pieces into hemi-shells which are then bonded together, and the other by sputtering Be with Cu dopant onto spherical plastic mandrels to build up a wall. This method allows for radial variation in the Cu dopant concentration, while the machining approach is best suited to a uniform doping level. For plastic, we have already made a down select, eliminating polyimide because its performance as an ablator has been seen to be significantly different from that predicted by simulations. The other polymer, GDP (glow discharge polymer or sometimes called plasma polymer) comes in both a normal (hydrogenated) and deuterated form. There are differences between them (besides the H or D) and these will be detailed. The choice between them will be determined in part by cryogenic measurement of the IR absorption spectrum of DT scheduled to occur in the next few months. An initial list of specifications for ignition targets exists. However these specifications are continuing to evolve. This is due to evolving plans for NIF's deliverable energy and to more refined design simulations. Many requirements are not well specified due to lack of knowledge of the effect on the implosion. These requirements include: grain size and texture, fill hole size, fill tube size, bond joint thickness, allowable porosity (size and number), diameter and wall thickness. Experiments are currently underway to assess the effect of grain size and texture, fill hole size, fill tube size, and bond joint thickness on the implosion. These parameters are being specified by simulation where possible. In cases such as bond joint thickness and fill hole size, the calculation methods are still under development. Completion of ignition capsule development will require final specifications.