低能氘离子束轰击固体靶产生的远程D-D核聚变现象研究

利用强流低能氘离子束轰击由吸氢金属形成的氘自吸收靶，研究固体内Ｄ－Ｄ聚变反应规律。并通过对实验测得的Ｄ－Ｄ聚变伴随粒子能谱，探索Ｄ－Ｄ聚变反应与靶材料结构的相关性。同时，利用氘团簇离子（ｄ＾＋３）氘核（ｄ＾＋）束轰击吸氘固体，研究固体内Ｄ－Ｄ聚变反应的特性。实验中观测到了伴随离子能谱中介于质子峰（３ＭｅＶ）和氚峰（１ＭｅＶ）之间的一个宽峰。结果分析表明，该峰是由固体靶内超出离子射程几倍至十几倍处发     

低剂量离子在物体样品中透射行为的研究

利用金硅面垒探测器测量低剂量率的Ｆ离子在生物组织样品（洋葱内表皮和芸豆种皮）中的透射能谱,用来研究荷能离子在生物样品中的能损和深度分布,实验中Ｆ离子能量为９００ｋｅＶ－６ＭｅＶ剂量率大约为１０＾４ｉｏｎｓ／ｓ·ｃｍ＾２。用ＳＥＭ观测样品在离子束轰击下可能发生的损伤,实验中测量了了不同能量离子样品中的透射能谱,利用ＳＩＮＲＡ对测量得到的透射能谱进行了拟合分析,并讨论了生物样品的特殊结构对透射能谱和离     

两种聚乙烯材料中的电子束辐照剂量分布测定---优化辐射加工工艺的一种实验方法

利用电子静电加速器和高频高压电子加速器，在１．０～３．０ＭｅＶ能量范围内，测定了两种聚乙烯材料中的剂量深度分布；比较了ＡＩ、Ｆｅ、Ｃｕ、Ｐｂ４种衬底金属板，对受辐照材料吸收剂量深度分布的影响；考察了材料中吸收剂量的边界效应。吸收剂量测量的总不确定度为７．８％。优化电子束辐射加工工艺是实现辐照产品质量控制的一种有用的实验方法。     

^16O弹性前冲测量氦的深度分布

利用１２ＭｅＶ的１６Ｏ离子弹性前冲测量（ＥＲＤ）方法，研究了以２０ｋｅＶ和４０ｋｅＶ注入４Ｈｅ的镀钛样品。通过分析ＥＲＤ能谱，得到了注入４Ｈｅ的深度分布，并与非卢瑟福背散射结果进行了比较。对４０ｋｅＶ注入的样品观察到有双峰分布，２０ｋｅＶ注入的样品没有双峰分布，实验结果与ＴＲＩＭ模拟计算结果进行了比较。     

ST—451液体闪烁体中子探测器效率的测量

利用伴随粒子飞行时间方法，通过测量１４．７ＭｅＶ中子在聚乙烯和碳样品上的次级中子谱，得到了在０．９９－１４．７ＭｅＶ能量范围内ＳＴ－４５１液体闪烁体中子探测器的探测效率值，其总误差＜４．７％，其中统计误差＜３．５％。     

氘—氚托卡马克等离子体中约束α分布的测量

在ＴＦＴＲ托卡马克氘－氚等离子体芯部，α密度为３×１０＾１６ｍ＾－３时，用光谱测量术观察了能量≤０．７ＭｅＶ的聚变产生的α粒子。在无锯齿放电期间，在ｒ／ａ＝０．３处所测得的能谱与基于碰撞输运所预计的能谱完全一致。在α源关闭之后，α热化期间时间分辨测量表明，分布函数衰减到较低能量是与经典慢化时间０．５ｓ一致的。     

70MeV质子加速器产生的白光中子源强度和能谱的计算

用７０ＭｅＶ质子束轰击厚靶可产生白光中子源。选用金属钨作厚靶材料，应用适用于几十ＭｅＶ能区的核反应模型程序计算了中子能谱和角分布。结果表明：７０ｍｅＶ质子束在钨厚靶中终止前有４．６％的质子发生了反应，２００μＡ的７０ＭｅＶ质子束流产生的中子总强度为１．０１×１０１４Ｓ－１，中子平均能量为４．２ＭｅＶ，１０ＭｅＶ以上的中子强度为１．１５×１０１３Ｓ－１，高能中子主要在朝前的小角度区发射。     

北京大学6MV串列静电加速器的运行及其应用

北京大学６ＭＶ串列静电加速器上建成４条束流输运线，加速＾１Ｈ，＾１２Ｃ，＾１６Ｏ，＾１９Ｆ，＾３５Ｃｌ，＾７９Ｂｒ等离子，并开展物理实验研究。首次利用Ｄ（＾１２Ｃ，ｐ）＾１３Ｃ核反应建立起高灵敏度的氘分析法；利用共振核反应＾１Ｈ（＾１９Ｆ，αγ）＾１６Ｏ分析材料中氢的深度分布；用重离子背散射分析超导材料ＹＢａ２Ｃｕ３Ｏ７－ｘ；用３５ＭｅＶ＾３５Ｃｌ和４５ＭｅＶ＾７９Ｂｒ的弹性前冲分析不同材料中的轻     

用CR—39固体径迹探测器测定重带电粒子的Bragg峰位

采用ＣＲ－３９固体径迹探测器，根据辐射损伤密度沿粒子的径迹分布规律，测定了经３、４ｃｍ空气降能和φ１ｍｍ孔准直的α粒子（５．１５ＭｅＶ）的Ｂｒａｇｇ峰位。对于通过３ｃｍ空气后能量降至～１．２ＭｅＶ的α粒子，在ＣＲ－３９中的Ｂｒａｇｇ峰位大约在７μｍ深度处，理论计算值在６．１４μｍ，实验值与理论值符合得较好。     

天然Ni和Fe（n,xp）核反应的双微分截面测量

用中国科学技术大学的多路望远镜系统，测量了天然Ｎｉ和Ｆｅ（ｎ，ｘｐ）反应在Ｅ＿ｎ＝１４．６ＭｅＶ能区的双微分截面，所测量的反应角为２５－１６５°，共１６个，质子出射能区为４－１４ＭｅＶ，并由此得到能谱、角分布和总截面。     

用~(14)N(d,α_1)~(12)C核反应研究注入氮在纯铁和GCr15钢中的深度分布

本文描述了利用~(14)N(d,a_1)~(12)C核反应测量固体样品表面层内氮原子含量及深度分布的方法。在Si_3N_4标准样品中,所得到的表面处的深度分辨为48nm。利用该分析手段,研究了在不同注入温度条件下,氮离子注入纯铁和GCr15钢的保留量及深度分布的变化情况。     

DEPTH PROFILING OF ~1H AND/OR ~4He IN SOLIDS BY ERD WITH ~(19)F IONS

1H or 4He depth profiling in 1H or 4He implanted silicon samples was performed by elastic recoil detection (ERD) with multicharged 19F ions at a small accelerator. Optimization of the experimental parameters such as incident ions energy and scattering geometry were calculated by computer simulation. Depth resolution of about 20-30nm at depth of 400nm for 1H and at depth of 300nm for 4He can be obtained, respectively.     

DETECTION AND DEPTH PROFILING OF ~(19)F USING RESONANCES IN THE ~(19)F(α,p) ~(22)Ne REACTION

Resonances in the reaction 19F (α ,p) 22Ne have been used to detect and depth profile 19F in solid targets. Incident alpha particles in the range 2100-2500 keV were used and protons were detected at θ=135° with a large solid angle surface barrier detector covered to stop elastically scattered alpha particles. This technique is a simple, nuclide specific probe and is particularly useful in detecting 19F in the presence of heavy elements such as GaAs where conventional Rutherford backscattering is ineffective. Examples using this technique on epitaxially grown thin films containing LaF3 layers will be presented.     

Detection system for depth profiling of radiotracers

A reliable and efficient detection system essentially needed in the depth profiling of radiotracers consisting of two large PIN-diode arrays has been constructed. The requirements put forward to the detector system and the ability of the PIN-diode array to meet these demands are discussed. A comparison to a conventionally used liquid scintillation detector is presented by measuring an as-implanted ³¹Si profile in amorphous T21 ceramic by both apparatuses.     

Depth of origin of atoms sputtered from crystalline targets

Recently, V.I. Shulga and W. Eckstein (Nucl. Instr. and Meth. B 145 (1998) 492) investigated the depth of origin of atoms sputtered from random elemental targets using the Monte Carlo code TRIM.SP and the lattice code OKSANA. They found that the mean depth of origin is proportional to N^−0.86, where N is the atomic density; and that the most probable escape depth is λ₀/2, where λ₀ is the mean atomic distance. Since earlier molecular dynamics simulations with small crystalline elemental targets typically produced a most probable escape depth of zero (i.e., most sputtered atoms came from the topmost layer of the target), we have carried out new molecular dynamics simulations of sputtered atom escape depths with much larger crystalline targets. Our new results, which include the bcc targets Cs, Rb and W, as well as the fcc targets Cu and Au predict that the majority of sputtered atoms come from the first atomic layer for the bcc(1 0 0), bcc(1 1 1), fcc(1 0 0) and fcc(1 1 1) targets studied. For the high-atomic density targets Cu, Au and W, the mean depth of origin of sputtered atoms typically is less than 0.25λ₀. For the low-atomic density targets Cs and Rb, the mean depth of origin of sputtered atoms is considerably larger, and depends strongly on the crystal orientation. We show that the discrepancy between the single-crystal and amorphous target depth of origin values can be resolved by applying a simple correction to the single-crystal results.     

CALCULATION AND OPTIMIZATION OF EXPERIMENTAL PARAMETERS IN ELASTIC RECOIL DETECTION (ERD)

Elastic recoil detection (ERD) proposed for the analysis of light elements in a heavier matrix is an appropriate method for its specialities. Optimization of experimental parameters in ERD such as scattering geometry and incident beam energy is very important when using a small accelerator with energy lower than 10 MeV. In this paper a computer program ERDAl is developed for the purpose, and is proved to be useful for practical handling of ERD experiments.     

快中子治癌束剂量特性研究

我国第一台中子治癌装置由３５ＭｅＶ质子＋Ｂｅ反应产生的快中子束已在临床中取得初步结果。其剂量测试系统的监测室积分电荷－标准体模内中子吸收剂量校正因子ｋ＿（ｃｏｒ）值，在标准源皮距（１３７，３ｃｍ）、标准射野（９ｃｍ×９ｃｍ）和深度９ｃｍ条件下测得，在半年内２０次测量的相对标准差为±０．６３％。本文研究了不同射野尺寸对水模体内中子束深部剂量曲线的影响，大的射野尺寸将获得较高深部剂量。对于上述标准射野和源皮距，１０ｃｍ深处相对水模体前表面的剂量为５２％，与美国费米实验室相近几何条件下测得的中子束的相时深部剂量（６３％）相近。离轴比为１０．５％，略优于费米实验室的（１４／）。