Color center formation in alpha-Al2O3 induced by high energy heavy ions

Single crystals of alpha-alumina were irradiated at room temperature with 1.157 (GeVFe)-Fe-56, 1.755 (GeVXe)-Xe-136 and 2.636 (GeVU)-U-238 ions to fluences range from 8.7 x 10(9) to 6 x 10(12) ions/cm(2). Virgin and irradiated samples were investigated by ultraviolet visible absorption measurements. The investigation reveals the presence of various color centers (F, F+, F-2(2+), F-2(+) and F-2 centers) appearing in the irradiated samples. It is found that the ratio of peak absorbance of F-2 to F centers increases with the increase of the atomic numbers of the incident ions from Fe, Xe to U ions, so do the absorbance ratio of F-2(2+) to F+ centers and of large defect cluster to F centers, indicating that larger defect clusters are preferred to be produced under heavier ion irradiation. Largest color center production cross-section was found for the U ion irradiation. The number density of single anion vacancy scales better with the energy deposition through processes of nuclear stopping, indicating that the nuclear energy loss processes determines the production of F-type defects in heavy ion irradiated alpha-alumina.

Color center formation in silica glass induced by high energy Fe and Xe ions

Silica glass samples were implanted with 1.157 GeV Fe-56 and 1.755 GeV Xe-136 ions to fluences range from 1 x 10(11) to 3.8 x 10(12) ions/cm(2). Virgin and irradiated samples were investigated by ultraviolet (UV) absorption from 3 to 6.4 eV and photoluminescence (PL) spectroscopy. The UV absorption investigation reveals the presence of various color centers (E' center, non-bridging oxygen hole center (NBOHC) and ODC(II)) appearing in the irradiated samples. It is found that the concentration of all color centers increase with the increase of fluence and tend to saturation at high fluence. Furthermore the concentration of E' center and that of NBOHC is approximately equal and both scale better with the energy deposition through processes of electronic stopping, indicating that E' center and NBOHC are mainly produced simultaneously from the scission of strained Si-O-Si bond by electronic excitation effects in heavy ion irradiated silica glass. The PL measurement shows three emissions peaked at about 4.28 eV (alpha band), 3.2 eV (beta band) and 2.67 eV (gamma band) when excited at 5 eV. The intensities of alpha and gamma bands increase with the increase of fluence and tend to saturation at high fluence. The intensity of beta band is at its maximum in virgin silica glass and it is reduced on increasing the ions fluence. It is further confirmed that nuclear energy loss processes determine the production of alpha and gamma bands and electronic energy loss processes determine the bleaching of beta band in heavy ion irradiated silica glass. (c) 2009 Elsevier B.V. All rights reserved.

一种低活化铁素体/ 马氏体钢的高能重离子辐照效应研究

Low-activation Ferritic/Martensitic steels are a kind of important structural materials candidate to the application in advanced nuclear energy systems.Possible degradation of properties and even failure in the condition of high-temperature and high helium production due to energetic neutron irradiation in a fusion reactor is a major concern with the application of this kind of materials.In the present work microstructural evolution in a 9Cr Ferritic/Martensitic steel(T92B) irradiated with 122 MeV 20Ne ions...中文摘要：低活化的铁素体/马氏体钢是先进核能装置(如聚变堆)的重要候选结构材料。在聚变堆实际工作环境下,由于高温和高氦产生率引起的材料失效是这类材料面临的一个重要问题。本项研究以兰州重离子加速器(HIRFL)提供的中能惰性气体离子束(20Ne,122 MeV)作为模拟辐照条件,借助透射电子显微镜,研究了一种低活化的9Cr铁素体/马氏体钢(T92B)组织结构的变化和辐照肿胀。实验结果表明,高温下当材料中晶格原子的撞出损伤和惰性气体原子沉积浓度超过一定限值时,材料内部形成高浓度的空洞,并且空洞肿胀率显著依赖于辐照温度和剂量;在马氏体板条界面及其它晶界处空洞趋于优先形成,并且在晶界交汇处呈加速生长。基于氦泡的形核生长与空洞肿胀的经典模型探讨了在不同辐照条件(He离子、Ne离子、Fe/He离子双束、快中子、Ni离子)下铁素体/马氏体钢中肿胀率数据的关联。

Sputtering induced by highly charged Pb-208(q+) bombardment on Al surface

Highly charged ions (HCls) carrying high Coulomb potential energy (E-p) could cause great changes in the physical and chemical properties of material surface when they bombard on the solid surface. In our work, the secondary ion yield dependence on highly charged Pbq+ (q = 4-36) bombardment on Al surface has been investigated. Aluminum films (99.99%) covered with a natural oxide film was chosen as our target and the kinetic energy (E-k) was varied between 80 keV and 400 keV. The yield with different incident angles could be described well by the equation developed by us. The equation consists of two parts due to the kinetic sputtering and potential sputtering. The physical interpretations of the coefficients in the said equation are discussed. Also the results on the kinetic sputtering produced by the nuclear energy loss on target Surface are presented.

Damage accumulation in gallium nitride irradiated with various energetic heavy ions

In this work a study of damage production in gallium nitride via elastic collision process (nuclear energy deposition) and inelastic collision process (electronic energy deposition) using various heavy ions is presented. Ordinary low-energy heavy ions (Fe+ and Mo+ ions of 110 keV), swift heavy ions (Pb-208(27+) ions of 1.1 MeV/u) and slow highly-charged heavy ions (Xen+ ions of 180 keV) were employed in the irradiation. Damage accumulation in the GaN crystal films as a function of ion fluence and temperature was studied with RBS-channeling technique, Raman scattering technique, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For ordinary low-energy heavy ion irradiation, the temperature dependence of damage production is moderate up to about 413 K resulting in amorphization of the damaged layer. Enhanced dynamic annealing of defects dominates at higher temperatures. Correlation of amorphization with material decomposition and nitrogen bubble formation was found. In the irradiation of swift heavy ions, rapid damage accumulation and efficient erosion of the irradiated layer occur at a rather low value of electronic energy deposition (about 1.3 keV/nm(3)),. which also varies with irradiation temperature. In the irradiation of slow highly-charged heavy ions (SHCI), enhanced amorphization and surface erosion due to potential energy deposition of SHCI was found. It is indicated that damage production in GaN is remarkably more sensitive to electronic energy loss via excitation and ionization than to nuclear energy loss via elastic collisions.

多普勒能移反冲距离法测核能级寿命

本文主要致力于建立一个用多谱勒能移反冲距离法测寿命的主要方法。对所设计加工的多谱勒能移反冲距离法测寿命的实验装置--PLUNGER的结构特点作了详细的说明，描述了用电容法测量和监视PLUNGER的靶与阻止膜间微小距离及其变化的实验，并从中得出零点距即靶与阻止膜间所能达到的最小距离为6-9#mu#m。用激光反射法测定了PLUNGER在运动中靶与阻止膜间的平行度的改变。还叙述了该PLUNGER装置用于~(13)P束轰击~(93)Nb靶的在束实验详细过程及数据处理，给出了~(120)Xe的基带各能级寿命及~(121)Cs、~(117)I的部分能级寿命。最后讨论了探测器的立体角效应、束流照射的热效应等对寿命测量的影响