木星系探测中多层材料的辐射屏蔽优化设计方法

与地球辐射环境相比，木星辐射带中的粒子辐射环境有能量高、通量大、能谱硬等特点，对木星探测器的辐射防护要求更高。航天器设计中常用的多层金属材料的防护效果取决于辐射环境、屏蔽层数量与厚度、屏蔽层叠放顺序等众多因素，因此采用数值方法进行设计十分困难，有必要开发智能屏蔽优化算法。文章结合遗传算法和MULASSIS多层屏蔽仿真程序，以屏蔽后的吸收剂量为优化目标，开发了多层材料辐射防护优化设计方法。利用该方法，得到一定重量指标约束下的最优屏蔽结构，其特点是将高低原子序数材料相结合，多为双层或三层结构，并把高原子序数材料放置在外侧。以远木点和近木点分别为25个和10个木星半径的赤道面轨道为例，当面密度为1 g/cm2时，最优屏蔽结构为0.829 mm铅和0.158 mm镁的双层结构，可将辐射造成的总剂量降低至120.3 krad(Si)/a，与传统铝屏蔽材料相比，可节省近43.6%的重量资源。本方法可用于指导未来木星探测的辐射防护设计。

Optimization design of radioprotection by multilayer materials in Jovian system exploration missions

The energetic particle radiation environment in the Jovian radiation belt is much higher than that in the Earth’s orbit in terms of the flux and energy levels. So that an appropriate radiation protection design is essential for the success of the Jovian orbiting mission. In the spacecraft design, multi-layer metallic materials are often adopted for the radiation protection. The protective effect is determined by a combination of the radiation environment, the number and the thickness of layers, and the stacking structure of the layers. Therefore, it is difficult to make a satisfactory scheme merely through numerical analysis methods. In this paper, we combine the genetic algorithm with the MU-LASSIS software and propose a method to determine the best structure of the multilayer shielding to minimize the total ionizing dose. With this method, the optimized shielding structure is obtained under the constraint of the total mass of the structure. The best structure is featured by the high-Z and low-Z materials combined, usually laid in double- or triple-layer, and the high-Z material layer is placed outside. With regard to the equatorial orbiting altitude of 10 RJ and 25 RJ for the periapsis and the apoapsis, respectively, the best protective structure under an areal density of 1 g/cm2 is that of a 0.829 mm lead layer combined with a 0.158 mm magnesium layer. The total ionizing dose after the shielding structure is 120.3 krad(Si)/a. Compared with the traditional aluminum shielding structure, about 43.6% of the mass can be reduced. This optimization method may be useful in the radiation protection design of the Jovian exploration missions in the future.