激光惯性约束聚变冷冻靶中低温下氘氚的相变热力学特性研究

Inertial confinement fusion (ICF) power has been envisioned as a viable solution for future world energy demands. Targets with thermonuclear fuel (hydrogen isotopes) play an important role in the ICF research field. Experiments have verified that the deuterium-tritium cryogenic target is the most hopeful target-type to achieve ignition. The ICF physical designs require smooth and uniform deuterium-tritium (DT) ice layers in a capsule to overcome the Rayleigh-Taylor instabilities during implosion. The production of (D-T) cryogenic target is, from the viewpoint of physical mechanism, actually a series of phase change processes, whose thermodynamic characteristics directly relate to the quality of the cryogenic target, such as the morphology and roughness of the ice layer inner surface. The current research in cryogenic target mainly focuses on the apparent characteristic of the ice layers, the related theoretical explanation and quantitative description is still penurious. Therefore, the phase change effect and thermodynamic process is investigated by both numerical simulating and experimental methods. The numerical simulating model is built up to investigate phase change effect in the D-T cryogenic target, such as seed nucleation and layering. Furthermore, experiments are carried out in the cryogenic system to verify the feasibility of the simulating model. The D-T phase change process at liquid hydrogen temperature such as seed nucleation, propagation and evolution of D-T solid distribution is monitored and characterized by the optical microscopy and x-ray radiography method. This research will be benefit for the deep understanding of some basic physical issues such as hydromechanics, heat and mass transfer, transport of multi-species in the production process of D-T cryogenic target. The study provides a theoretical basis to solve some technical problems in cryogenic target. It will help to improve the R&D level of D-T cryogenic target and thus lays a foundation for the ICF research in China.

激光惯性约束聚变(ICF)是解决未来能源需求的重要途径，热核靶丸在ICF的研究中具有重要地位，氘氚冷冻靶是目前已被证实的最有利于实现点火的靶型。为了抑制内爆时的流体力学不稳定性，需要在靶丸内表面形成均化光滑的氘氚冰层。冷冻靶的制备是氘氚燃料在低温下的一系列相变过程，其热力学特性直接关系到冰层的表面形貌、粗糙度等性能。现有冷冻靶的研究侧重于关注冰层的表观特性，对实验现象缺少理论解释和定量描述。本项目结合数值模拟和实验对冷冻靶中氘氚的相变热力学特性进行研究。建立了关于冷冻靶的相变热力学数值仿真模型，获得影响氘氚冰层形核生长和分层等相变物理过程的关键因素。在氘氚冷冻靶低温实验平台上开展实验，通过表征手段获得低温下氘氚的相变过程，并和数值模拟结果进行比较，验证模型的可靠性。本研究有助于深化对冷冻靶制备中热物理相关基础问题的认识，将有利于提高氘氚冷冻靶制备水平，为我国ICF研究的顺利开展打下基础。