MeV微集团束与物质的相互作用

简述了有关MeV微集团离子束与物质表面相互作用研究的概况．介绍了在北京大学技术物理系和重离子物理所１．７ＭＶ串列加速器上开展的有关实验研究及取得的初步结果． The recent development on investigation of MeV microcluster beam interaction with matter is outlined. And based on 5SDH 2 Pelletron of Peking University, some relative experimental results, such as identification and Rutherford backscattering measurement of MeV carbon cluster ions, stopping power of MeV silicon microcluster ions in Al film, damage producted in silicon by MeV silicon microcluster irradiation, etc. are briefly introduecd.     

Optical Waveguide Formed in Yb：KLu（WO4）2 Crystal by 6.0 MeV O^＋ Implantation

A planar optical waveguide is formed in monoclinic double rare-earth-tungstate laser crystal Yb：KLu（WO4）2 by 6.0 Me V oxygen ion implantation with a dose of 2 × 10^16 ions/cm^2 at room temperature. Subsequently, annealing at 300℃ for an hour in air is performed on the sample to decrease colour centres to improve the thermal stability of the waveguide. The refractive index profiles of the waveguide are reconstructed by an effective refractive index method. Dark modes of the waveguide are observed at wavelengths of 633 nm and 1539 nm. TRIM＇98 is used to simulate the damage profile caused by the implantation process. It is found that the refractive index change may be mainly due to the damage induced by the nuclear energy loss.     

加速器束流脉冲化及氢二次离子发射研究

详细介绍了快速高压晶体管开关在加速器束流脉冲化和用于二次离子测量的加速器飞行时间谱仪上的应用. 利用飞行时间法研究了碳纳米管在不同能量的Si和Si2团簇离子轰击下氢二次离子的发射. 实验结果表明， 在每个原子质量单位的速度为2.5×108 cm/s以上， Si和Si2离子引起的氢二次离子的发射主要受电子阻止过程控制； 在每个原子质量单位的速度为2.5×108 cm/s以下和Si2团簇离子轰击的情况下， 氢二次离子的发射产额明显增加， 团簇离子在靶表面的核能损增强效应起主要作用. The application of Fast High Voltage Transistor Switches (HTS) in pulsed ion beam and the time of flight(TOF ) setup is described. Secondary ion emissions from carbon nanotubes under bombardments of MeV Si and Si2 clusters are measured by using TOF. The measurements indicate that the yield of the secondary ion emissions of hydrogen increases with increasing energy of Si and it is attributed to the electronic processes. The yield of the secondary ions of hydrogen decreases with increasing energy of Si2 clusters and the enhancement of nuclear energy loss of cluster constituents at the surface of sample plays a more significant role in the secondary ion emission of hydrogen at the low energies.     

Ion－Implanted Waveguides in a Nd^3＋－Doped Silicate Glass

Monomode enhanced-index Nd^3 -doped silicate glass waveguides fabricated by ion implantation are reported.The Nd^3 -doped silicate glass was implanted by 3.0 MeV B^ ions, 3.0 MeV 0^ ions and 4.5 MeV Ni^2 ions,respectively. A prism-coupling method was carried out to measure dark modes in the Nd^3 -doped silicate glassusing a model 2010 prism coupler. The moving fibre method was applied to measure the waveguide propagationloss. After a moderate annealing, the 3.0-MeV B^ -ion implanted waveguide loss is about 3.54 dB/cm; the 3.0-Me V O^ -ion implanted waveguide loss is about 5.36 dB/cm; and the 4.5-MeV the Ni^2 -implanted waveguide lossis about 7.55dB/cm. The results show that with the increasing ion mass, the loss in implanted waveguide isincreased.     

A MICROSCOPIC MECHANISM OF LOW TEMPERATURE HELIUM RELEASE

⁴He ions of various energies and at various doses were implanted into three kinds of samples: TiH₂ films, high purity Ti pieces as-received and after hydrogenation. Thermal release of helium was monitored in situ by proton-enhanced backscattering. Low-temperature helium release was observed at T≤573K. Single jump model was used to calculate the active energies for the release. Based on the observations, a mechanism of helium cluster vacancy complex (He_mV_n-V_i) for low temperature helium release is proposed.     

离子注入法形成的LiTaO3平板光波导的特性分析

用能量为２．８ＭｅＶ、剂量为１．４×１０１６ｉｏｎ／ｃｍ２的Ｈｅ＋在室温（３００Ｋ）下注入到晶体材料ＬｉＴａＯ３中，形成了离子注入平板光波导。用棱镜耦合法观察和测量了ＬｉＴａＯ３波导导模的分布，并对退火前后的ＬｉＴａＯ３波导的折射率分布进行了计算和比较。利用背散射／沟道技术分析了由于Ｈｅ＋的注入而引起的波导表面的损伤。     

Comparison of Secondary Ion Emissions from Carbon Nanotubes under Bombardments of MeV Si and Si2 Clusters

The emission yields of H, H2, H3 and heavy ions from carbon nanotubes under bombardments of Si and Si2 clusters in an energy range of 0.3-3 MeV per atom are measured by using the time-of-flight technique (TOF). The emission yields of the secondary ions increase with increasing energy of Si and the electronic stopping processes play an important role. The enhanced emission yields of secondary ions induced by Si2 clusters at the low energies are clearly seen and attributed to the vicinage effect of the nuclear collision processes of cluster constituents and the secondary ion emissions are still dominated by electronic stopping processes at high energies.     

区熔硅中质子注入缺陷的EPR研究

在质子注入的n型区熔硅中,电子顺磁共振(EPR)测量观察到一个新的缺陷,命名为Si-PK5.该缺陷具有以〈111〉为对称轴的三角对称,其顺磁参数为S=1/2,g_∥=2.0078,g_⊥=2.0174.根据Lee和Corbett 以及Sieverts 提出的缺陷分类法,Si-PK5属键心间隙型结构.此外,还观察到两个文献已报道过的缺陷:Si-S1和Si-S2. 对Si-S2,首先看到由²⁹Si核引起的超精细分裂.