X光辐射在泡沫介质中超声速传输研究进展

X光辐射输运过程通过光子的发射与吸收使能量在介质内进行再分配,而光子的辐射和吸收过程对从介质内出射的能谱产生十分显著的影响。辐射输运由积分-微分方程来描述,得到它的解极其困难,这是因为此方程依赖于局域和非局域的条件。当外加的非局域的X光辐射场作用在介质上一个强的X光辐射能流时,介质的局域温度和密度将影响X光的吸收和发射。本文将对辐射输运的方程和基本理论进行阐述,并对辐射超声速传输的实验结果进行评述。首先,介绍辐射在介质中的传输的理论基础以及简化分析模型;其次,对辐射在介质中扩散超声速输运进行解析分析,我们首次导出辐射的超声速传输条件下的辐射能流与物质能流之比与马赫数和光学厚度的定量关系;最后,介绍国外的主要实验结果,同时也给出我们近期的研究结果。我们的实验结果表明,不同能区的光子因辐射不透明度不同使得在介质中的传播时间不同,并且实验测出光学厚度。

PROGRESS IN RESEARCH OF SUPERSONIC TRANSPORT OF RADIATION WAVE IN RADIATIVELY HEATED FOAM TARGETS

Radiation transport redistributes energy within a medium through the emission and re absorption of photons. These processes also have a pronounced effect on the spectrum of radiation that escapes the medium. Radiation transport is described by an integro-differential equation. The solution to this equation is particularly difficult because it depends on local and nonlocal conditions. The local material temperature and density affect the absorption and emission of radiation while an external non-local radiation field can significantly impact the energy flux. This review paper covers the basic theory and equation describing radiation transport, experimental examples of supersonic transport phenomena. First, the theory basis and simple model of supersonic transport of radiation wave in low density medium are introduced. Second, at first time, we have derived the expression, in which the ratio of the radiative energy flux to the material energy flux is directly proportional to Mach number M and optical depth r under the condition of diffusion approximation and supersonic transport of radiation wave. Finally, the experimental results about supersonic transport of radiation wave measured by many laboratories including ours are presented. Our results indicate that the transport delays of the photon groups at different energies through foam are different, because their opacities vary with photon energy.