双能量质子束辐照晶闸管的研究

在制造快速晶闸管的过程中电子辐照已被广泛采用 ,但是 ,电子辐照在提高开关速度的同时 ,也会引起正向导通压降的增大。采用高能质子辐照既能提高开关速度又能尽量降低正向导通压降。由于一定能量的质子在物质中的射程是一定的 ,质子辐照造成缺陷或复合中心分布在一定的狭窄区域 ,在那里 ,缺陷可以有效地增加开关速度又不显著增加导通压降。本文介绍用HI- 13串列加速器产生的质子束辐照晶闸管的工作。实验表明 ,双能量质子束的辐照效果是非常优越的。     

强流质子直线加速器中束晕现象研究

从束流包络方程与单粒子运动方程联立模型出发，考虑了纵向能量方程的耦合，研究了强流质子直线加速器中的束晕现象。采用相交间的Ｐｏｉｎｃａｒｅ截面方法和实空间Ｐｏｉｎｃａｒｅ截面方法，研究了周期聚焦系统失配的情况下束晕的形成以及加速对束晕形成的影响。     

Ar离子束辐照下多壁碳纳米管网络的导电性增强

用Ar离子束辐照800K高温下的多壁碳纳米管（MWCNT）网络,注量为2×1016/cm2时,MWCNT网络的导电性提高～80%。实验结果表明,离子束辐照可通过在多壁碳纳米管间的引入连接改善多壁碳纳米管间的电学接触,制备高导电性的透明碳纳米管网络。     

基于多元线性回归模型的中性束质子比分析

中性束质子比的高低对其注入等离子体后的加热效果具有重要的影响。实验中,强流离子源的灯丝电压、弧压、进气量等宏观运行参数决定了中性束质子比的大小。以东方超环中性束注入测试台束引出实验为基础,利用多元线性回归模型对引出中性束质子比进行分析,建立了影响中性束质子比的预测方程,并对该模型的正确性进行了检验。结果表明,中性束质子比可利用以灯丝电压和弧压为自变量的多元线性回归模型进行分析,灯丝电压是影响质子比的关键参数,弧压次之。     

多壁碳纳米管γ辐照后的化学修饰

本工作用^60Co γ射线辐照多壁碳纳米管,再对其进行有机化学修饰,每步化学处理的产物都用红外和喇曼光谱表征。修饰后多壁碳纳米管的元素分析和热重分析表明,连接在多壁碳纳米管上癸胺的浓度随γ辐照剂量的增加而增加,这与辐照所致碳纳米管结构缺陷有关。与未辐照进行化学修饰的碳纳米管相比较,辐照后修饰的多壁碳纳米管在丙酮、四氢呋喃等有机溶剂中的溶解度明显提高。这一研究为碳纳米管的功能化修饰及其应用提供了新思路。     

MeV离子辐照聚酰亚胺的化学结构及电性能转变

在室温真空条件下,用北京大学离子注入机提供的3 MeV Si~+对厚度大约25μm的电绝缘聚酰亚胺(PI/Kapton)进行了表面改性,通过紫外可见光谱分析(UV/Visible)、傅立叶转换红外光谱分析(FTIR)及电性能测量,研究了不同离子注量(1×10~(12)—1×10~(15)cm~(-2))下注入层中聚酰亚胺各官能团的化学降解及石墨化结构转变机制。红外结果表明,官能团随离子注入量的增加指数降解,并通过实验点的拟合给出了典型分子键的损伤截面。辐照后聚合物的导电性发生了巨大变化,在我们的实验中,聚酰亚胺的面电阻与未辐照样相比下降了近10个数量级,呈现出半导体的电特性。紫外光谱中吸收边缘从紫外到可见区的红移表明了光能隙的逐渐减小,这是由于芳香团尺寸的增加而引起的。     

多束系统对12Cr-ODS钢辐照损伤协同效应的研究

室温下用不同种类的离子束对12Cr-ODS钢进行辐照。辐照前后12Cr-ODS钢的力学性能发生了明显变化,主要表现为辐照肿胀和辐照硬化,其中三束辐照下材料有最大的肿胀和最小的硬化。结合TEM照片对材料的辐照变化进行了分析。对材料进行拉曼光谱的测量,发现有碳析出现象,并且把碳峰的强度分布与辐照损伤分布进行了相互关联。本文为12Cr-ODS钢在实际反应堆中的应用积累了实验数据,明确了协同作用对核材料辐照损伤的影响。     

γ辐照后MWNTs的水溶性修饰

为开展碳纳米管的生物效应研究,多壁碳纳米管经γ辐照后与葡糖胺进行共价连接,得到水溶性较好多壁碳纳米管。拉曼光谱显示,γ辐照影响了多壁碳纳米管的表面结构,在其表面产生了一定量的缺陷。元素分析和热重分析表明,经过γ辐照后修饰的多壁碳纳米管表面连接了更多的葡糖胺,且其浓度随γ辐照剂量的增加而增加,结果导致多壁碳纳米管在水中的溶解度相比未辐照进行修饰的多壁碳纳米管有明显提高。利用γ辐照后多壁碳纳米管表面缺陷增多,为碳纳米管的修饰和进一步应用提供了新的思路。     

扫描式质子束剂量分布成像仪的研制及性能分析

在重离子癌症治疗技术中,保证重离子束的质量（均匀性、束斑大小和位置、能量等）非常重要。为满足临床对重离子束质量的要求,本文设计了一种新型质子束剂量分布成像仪。该剂量分布成像仪基于闪烁屏、镜面反射屏与光学信号采集装置,将重离子束通过硫氧化钆闪烁屏转化为可见光,通过采集可见光信号,对重离子束予以质量控制。同时通过精密的电动位移平台对闪烁屏、镜面反射屏与光学信号采集装置的相对位置进行遥控从而调整设备视野。结果表明,该剂量分布成像仪在布拉格峰后沿的能量分辨率为0.22 mm等效水深,空间分辨率为0.35 mm,对单一光源响应的均匀性在图像视野中心10 cm×10 cm的区域内为±3.5%,并可通过算法对测量结果进行修正。该剂量分布成像仪能完成对重离子束质量的各项关键指标的测试,可用于医用质子束的质量控制。     

The evolution of hydrogen from proton irradiated glassy carbon

Glassy carbon was irradiated with 15 keV H⁺ ion beam. It was observed that the implanted hydrogen is unstable in material and evolves as H, H₂ and H₂O. Post-irradiation evolution of H, H₂ and H₂O from proton irradiated glassy carbon was monitored by temperature programmed desorption (TPD) in the period of 30 days. In between irradiation and TPD measurements the irradiated samples were stored in air. The evolution of the molecular hydrogen, although the protons are implanted deeply below the surface of the disordered glassy carbon, proceeds over the same mechanism as in the case of low-energy H-atoms chemisorbed on the very surface of an ideal graphite structure.     

Use of a line focus of a quadrupole multiplet for irradiating millimeter length lines

We have developed a new method of irradiation suitable for uniformly irradiating long, straight lines for waveguide and channel fabrication in semiconductors and polymers. This is achieved by exciting the quadrupole lenses of a nuclear microprobe in a manner such that the beam is focused in one plane but highly defocused in the orthogonal plane. This method requires no surface mask and since the beam is not scanned, it produces uniformly-irradiated patterns. This approach has been used for rapid exposure of lines 8 mm in length with widths of about 3 μm in silicon and 1.5 μm in polymethyl methacrylate.     

Proton beam micromachined resolution standards for nuclear microprobes

The quest for smaller spot sizes has long been the goal of many nuclear microprobe groups worldwide, and consequently there is a need for good quality resolution standards. Such standards have to be consistent with the accurate measurement of state-of-the-art nuclear microbeam spot sizes, i.e. 400 nm for high current applications such as Rutherford backscattering spectrometry and proton-induced X-ray emission, and 100 nm for low current applications such as scanning transmission ion microscopy or ion beam-induced charge. The criteria for constructing a good quality nuclear microprobe resolution standard is therefore demanding: the standard has to be three dimensional with a smooth surface, have an edge definition better than the state-of-the-art beam spot resolutions, and exhibit vertical side walls. Proton beam micromachining (PBM) is a new technique of high potential for the manufacture of precise 3D microstructures. Recent developments have shown that metallic microstructures (nickel and copper) can be formed from these microshapes. Prototype nickel PBM resolution standards have been manufactured at the Research Centre for Nuclear Microscopy, NUS and these new standards are far superior to the 2000 mesh gold grids currently in use by many groups in terms of surface smoothness, vertical walls and edge definition. Results of beam resolution tests using the new PBM standards with the OM2000 microprobe end station/HVEE Singletron system have yielded spot sizes of 290 nm×450 nm for a 50 pA beam of 2 MeV protons.     

EB预辐照对制备PANACF表面形貌的影响

提出了利用电子束（electron beam, EB）预辐照聚丙烯腈基纤维（polyacrylonitrile-based fiber, PANF）后再进行炭化活化制备聚丙烯腈基活性炭纤维（polyacrylonitrile-based activated carbon fiber, PANACF）的方法。吸收剂量为160 kGy并用w=10%KOH溶液浸渍30 min的PANF在450 ℃下模拟炭化活化30 min后,SEM分析显示其表面出现了与未辐照PANF不同的密集的蜂巢状结构,其BET法比表面积（specific surface area, SSA）约为未辐照样品的9倍,BJH法计算结果显示其为孔径分布集中在2～10 nm的介孔材料。该结果表明,EB预辐照对制备PANACF的表面形貌具有调控作用。     

GMR薄膜抗辐照性能研究

研究了两种不同材料构成自旋阀结构的巨磁电阻 (Giant magneto resistance,GMR)多层膜受质子辐照、电子辐照和γ射线辐照的影响。实验结果表明,辐照会引起磁电阻率的略微下降,但降幅均低于10%,并且GMR薄膜的矫顽力和交换场并不受辐照的影响。对比发现,GMR元件受太空环境中以质子辐射为主的影响非常小,这表明GMR元件在空间应用中具有广阔的前景。     

Creation of 3D microsculptures in PMMA by multiple angle proton irradiation

In recent years the technique of proton beam writing has established itself as a versatile method for the creation of microstructures in resist materials. While these structures can be almost arbitrary in two dimensions, the creation of genuine 3D structures remains a challenge.At the LIPSION accelerator facility a new approach has been developed which combines aspects of ion beam tomography, so far solely an analysis method, with proton beam writing. Key element is the targeted irradiation from multiple angles in order to obtain a much broader range of 3D microstructures than has hitherto been possible.PMMA columns with a diameter of ∼90 μm were used as raw material and placed in an upright position on top of a rotational axis. Using 2.25 MeV protons patterns corresponding to the silhouettes of the desired structures were written from two or more directions. In a subsequent step of chemical etching irradiated portions were dissolved, leaving behind the finished 3D sculpture.Various objects have been created. For the demonstration of the method a 70 μm high model of the Eiffel tower has been sculpted by irradiation from two angles. Using irradiation from three angles a 40 μm wide screw with right-handed thread could be crafted which might find applications in micromachining. Also, a cage structure with a pore size of ca. 20 μm was written with the intention to use it as a scaffold for the growth of biological cells.     

GaAs太阳电池引入量子阱结构后抗辐射性能的变化

利用2×1.7MV串列静电加速器提供的质子束模拟空间环境辐射,对引入量子阱GaAs太阳电池和无量子阱GaAs太阳电池进行2MeV质子注量为1×109—2×1013cm-2的辐照,通过电池I-V特性和光谱响应测试,研究分析了它们的辐射效应。结果表明这两种电池的Isc、Voc和Pmax的衰降幅度均随辐照注量增加而增大;而相同注量的辐照,引入量子阱GaAs太阳电池电性能衰降幅度要比无量子阱GaAs太阳电池的大。经2×1013cm-2质子辐照后,引入量子阱GaAs太阳电池光谱响应在400—1000nm整个波段有明显衰降,且长波区（900—1000nm）的量子阱特性消失。量子阱结构的引入使GaAs太阳电池的抗辐射性能下降。     

利用粒子辐照技术实现碳纳米管向金刚石的转变

采用低能氢等离子体和中能C+离子束辐照技术相结合的方法,实现了碳纳米管向金刚石纳米晶粒的转变,完成了一个从有序（碳纳米管）到无序（无定形碳纳米线）再到有序（金刚石纳米晶）的转变过程。利用透射电子显微镜（TEM）、选区电子衍射（SAD）和拉曼光谱（Raman）等研究了晶粒的微观结构,并对纳米金刚石晶粒的生成机理进行了初步探讨。