高功率CaO/W/RVCF复合靶的设计与制备

为利用质子轰击⁴⁰Ca靶产生放射性核束³⁷K，本文系统研究了⁴⁰Ca靶的设计、制备和模拟的全过程。综合考虑反应截面、靶材料的丰度、熔点、蒸汽压和短扩散路径等，确定选择CaO作为靶材料，高孔隙率的网状玻璃碳纤维(RVCF，reticulated vitreous carbon fiber)作为基衬材料。采用PC（paint coating）法将CaO材料沉积在RVCF基衬上，为防止高温下CaO与RVCF发生化学反应并降低靶材料的抗高温性能，在沉积CaO靶材料前采用CVD（chemical vapour deposition）法对RVCF基材沉积1层1~2 μm厚的W保护层。根据质子束轰击复合靶的能损计算与分析结果，设计了靶室筒内装入厚靶的结构和靶室筒的散热结构。最后采用Comsol计算程序模拟分析了靶及靶室的温度分布，得出了此厚靶在75 MeV质子束入射时能承受的最大束流功率为7.5 kW。

Design and Preparation of High-power CaO/W/RVCF Compound Target

The thick CaO targets were investigated for the radioactive ³⁷K ion beam generation by the ⁴⁰Ca(p, α)³⁷K reaction. The CaO targets are the low-density, fibrous, highly permeable target materials. And they form the fast diffusion-release, mechanically and thermally stable production targets for the radioactive ³⁷K ion beam research applications. The low-density reticulated vitreous carbon fiber (RVCF) was used as the target matrix. The protective W layer with thickness of 1.2 μm was pre-coated onto the matrix by the chemical vapour deposition technology to prevent the undesired reaction process at a relatively high temperature. The CaO target material was deposited onto the W/RVCF matrix by the paint coating technology. The thickness of every part for the CaO/W/RVCF compound target was designed according to the calculation results of the energy loss and cross-section. The radiating structure of the target chamber was also designed and machined. The temperature distributions of the compound target and target chamber bombarded by different proton beam powers were simulated by the Comsol multiphysics code. The maximum proton beam power bombarding onto the CaO/W/RVCF compound porous target was found to be 7.5 kW for the present radiating structure of the target chamber.