加速器联机装置运行状况

Accelerator-TEM interface facility and application

2008年武汉大学加速器联机系统初步建成,200 kV离子注入机至透射电镜束线进行了运行调试,开展了气体离子注入单晶Si、GaAs、Ag纳米晶和超临界反应堆材料(C276和6XN)的原位结构研究。结果表明,样品在注入至一定剂量时发生明显多晶和非晶化,单晶Si出现非晶化的临界剂量在10^(14) cm^(-2)。C276材料经1×10^(15)cm^(-2)的Ar离子辐照后,产生尺寸3-12 nm的位错环,其密度随剂量提高而增大,至5×10^(15)cm^(-2)出现多晶,剂量超过3×10^(16) cm^(-2)出现非晶化。在加速器-电镜联机光路上安装在线RBS靶室对离子束辐照材料进行元素成分和晶格定位测试。靠近电镜端安装50 kV低能离子源,开展核材料中氦泡形成过程的原位观测。对RBS/C装置进行数字化改造,用Labview控制系统运行,目前可进行计算机控制的背散射沟道测试。

An accelerator-TEM interface facility has been established at Wuhan University in 2008. The system consists of an H800 TEM linked to a 200 kV ion implanter and a 2× 1.7 MV tandem accelerator. Nitrogen ions at 115 keV were successfully transported from the implanter into the TEM chamber through the interface system, and the ion currents measured at the entrance of the TEM column were between 20 and 180 hA. Structural evolution caused by ion irradiation in Si, GaAs, nanocrystal Ag was observed in situ. The in situ observation showed that the critical implantation dose for amorphization of Si is 10^144 cm^2. The nuclear material C276 samples implanted with 115 keV Ar^＋ was also studied, and dislocation loops sized at 3-12 nm were clearly observed after implantation to doses of over 1 × 10^15 cm^-2. The density of the loops increased with the dose. Evolution to polycrystalline and amorphous structures were observed at 5 × 10^15 cm^-2 and 3 ×10^16 cm^- 2 respectively. An in situ RBS/C chamber was installed on the transport line of the accelerator-TEM interface system. This enables in situ measurement of composition and location of the implanted species in lattice of the samples. In addition, a 50 kV low-energy gaseous ion generator was installed close to the TEM chamber, which facilitates in situ TEM observation of helium bubbles formed in helium-implanted materials.