西安脉冲堆127I嬗变计算方法与实验验证

为了开展129I的热中子嬗变的研究,在西安脉冲堆上开展了127I靶件辐照实验。以探索实验条件,对127I靶件的嬗变率进行了蒙特卡罗计算,并与实验测量值进行了比对。利用NJOY程序,以ENDF/B VII.0库为基础,制作了127I在西安脉冲堆堆芯辐照温度下的MCNP格式截面库,与MCNP自带库(ENDF/B VI.2)同温度下截面库进行了比较,在不可分辨共振区做了改进,使用新制的截面库,利用MCNP程序对ORIGEN2数据库中的127I辐射俘获截面进行了修正,结合ORIGEN2程序分析了127I靶件在西安脉冲堆实际辐照后的嬗变率和核素的变化,研究了中子能谱和辐照时间对靶件嬗变计算的影响。使用MCNPX自带的燃耗模块CINDER90对127I靶件的嬗变情况进行模拟,结果与ORIGEN2基本一致,与实验数值有2%~3%的偏差,主要原因是MCNP计算中子通量密度存在误差。     

小型加速器质谱系统研制及分析技术研究

加速器质谱(AMS)是测量长寿命放射性核素灵敏度最高的分析技术,在环境、地质、考古、物理等领域有着广泛应用。近年来,AMS装置的小型化在国际上得到了很大发展。为了研发小型化AMS装置及其分析技术,中国原子能科学研究院分别自主研制了加速电压为0.2 MV的单极型AMS装置和端电压为0.3 MV的串列型AMS装置。基于研制的单极型AMS装置,成功开展了14C的高效传输和本底排除技术研究,实现了14C的高灵敏测定,14C/12C的测量灵敏度达到2×10–15;利用研制的串列型AMS装置,开展了低能量下129I的气体剥离条件、本底排除和探测方法研究,建立了129I的高效传输和高灵敏测量方法,129I/127I的测量灵敏度为1×10–14。这是国内首次研制成功小型AMS装置,为AMS国产化奠定基础。     

浅谈加速器质谱小型化进程及应用

自上个世纪七十年代以来,加速器质谱技术在放射性核素丰度分析方面取得了巨大的成绩,特别是一些半衰期较长的放射性核素,例如10Be、14C、26 Al、36Cl、129 I,这些放射性核素可以被利用到生物,考古学,地质学等一系列领域。随着年代的发展,加速器质谱仪的体积和能量都经历了由大到小的变化,本文就国内外加速器质谱仪的发展过程,结合广西师范大学正在筹建的桌面化加速器质谱仪,为大家阐述加速器质谱仪的发展过程及部分应用。     

电感耦合等离子体质谱仪同时测定地下水中的溴和碘

研究并建立了电感耦合等离子体质谱仪（ICP-MS）同时测定地下水中溴、碘元素的方法。使用0.025%NH3.H2O作为测定介质,该方法线性范围宽,检出限为：79Br为0.02μg/L;127I为0.4μg/L。加标回收率在94.0%—102.4%之间。     

ICF分解实验用双介质调制靶的研制

为了研究惯性约束聚变(ICF)实验用靶丸不同密度界面的流体力学不稳定性增长,设计并制备了聚苯乙烯(CH)/碳气凝胶(CRF),CRF/硅气凝胶(SiO2)和CH/Al三种双介质调制靶。采用溶胶-凝胶工艺制备了密度分别为250和800mg/cm3的CRF气凝胶薄片;采用激光微加工工艺分别在两种不同密度的CRF薄片和工业用纯Al箔上引入调制图形;采用旋涂工艺在Al箔和CRF薄片(250mg/cm3)的调制表面制备一层CH薄膜,得到CH/Al和CH/CRF双介质调制靶,采用溶胶-凝胶工艺在CRF薄片(800mg/cm3)表面制备一层低密度SiO2气凝胶,得到CRF/SiO2双介质调制靶。采用电子天平、扫描电子显微镜、工具显微镜和台阶仪对所制备的CH/CRF,CRF/SiO2和CH/Al三种双介质调制靶进行靶参数测量。结果表明:三种双介质调制靶层与层之间结合紧密,界面清晰,调制图形为正弦,靶参数测量准确。     

驱动堆中长寿命核废料碘的嬗变研究

利用理论模拟和实验手段对加速器驱动的快中子堆消除常规反应堆排放的核废料碘进行了研究.实验中,利用加速器加速质子使其能量达到1.0GeV,并轰击重金属铅靶,利用靶中产生的次级中子诱发核废料¹²⁹I的嬗变,使其嬗变为稳定同位素¹³⁰Xe.对实验嬗变效率进行了理论模拟验证,进而拓宽到研究的驱动堆体系中.堆芯区的核燃料为乏燃料铀和钚,靶和初级热交换剂为液态铅.     

高分辨的弹性反冲探测分析技术

在中国原子能科学研究院HI－13串列加速器上建立了一套高分辨的弹性反冲探测分析技术,用高质量的127I重离子束轰击薄膜或块材靶样品,利用Q3D磁谱仪及其焦面探测器和纵向型双向型双电离室ΔE－E望远镜探测器两套探测系统,在前角区测量了靶中各种元素的反冲能谱,利用卢瑟福散射截离子在靶材料中的阻止本领,将能谱转换成元素的深度分布,利用Q3D磁谱仪系统,对C和H等轻元素的分析得到纳米级的深度分频谱,用ΔE－E望远镜探测器可同时得到靶材料上从轻至中重各种元素的深度分布,其深度分辨率达0－30nm。     

类氦C离子诱发不同金属厚靶原子的K-X射线

利用中国原子能科学研究院HI-13MV串列加速器上提供的动能为15—55 MeV的类氦C离子分别轰击Fe, Ni, Nb和Mo金属厚靶,采用HpGe探测器测量了K-X射线,获得了相应的K-X射线的发射截面.本文中由于各个靶原子外壳层电离度的不同,类氦C离子与Fe, Ni靶原子相互作用发射的K_β与K_α X射线的分支强度比随入射离子动能增加而减小,而Nb, Mo靶原子发射的K-X射线分支强度比变化不明显.利用厚靶截面公式计算了靶原子K-X射线的发射截面,并与不同的理论模型及质子的结果进行了对比.结果表明随类氦C离子动能的增大, Fe, Ni靶原子发射的K_β与K_α X射线的总产生截面与考虑多电离的两体碰撞近似修正模型最为符合Nb, Mo靶原子发射的K_β与K_α X射线的总产生截面与平面波恩近似模型的理论值最为接近.质子与单核子C离子能量相同时,质子比类氦C离子激发不同靶的K-X射线产生截面约小3个数量级.     

19F+93Nb重离子耗散碰撞中截面测量的不可重复性

完成了¹⁹F+⁹³Nb重离子耗散碰撞激发函数的两次独立测量.束流¹⁹F⁸⁺的入射能量100—108MeV,能量步长250keV;两次测量中分别使用了厚度为70和71μg/cm²的⁹³Nb靶,其它宏观实验条件(例如,入射能量及能量步长,探测器及其探测角度,加速器、电子学以及数据获取系统的参数选取等等)则保持完全相同.实验结果表明,两次测量所得到的耗散产物截面的激发函数的不平滑结构具有不可重复性.这一实验结果支持了最近提出的理论预言:“在复杂量子碰撞中存在对初始条件的极端敏感性与混沌运动.”     

介质壁加速器用固态脉冲形成线设计与实验

设计和研制了一种CaO-TiO2-Al2O3复合陶瓷平板固态脉冲形成线,以期用于介质壁加速器。该脉冲形成线的几何参数为:陶瓷介质长度300mm,宽度15mm,厚度1mm;银电极长度280mm,宽度2mm。电性能参数为:相对介电常数约23.5,特征阻抗约26Ω,电长度约4.5ns,直流耐压场强大于20kV/mm,在μs量级上升时间的脉冲电压下绝缘强度大于25kV/mm。该固态脉冲形成线设计兼顾了光导开关的使用要求、高梯度绝缘子的设计指标、带电粒子束的输运及加速器的结构设计要求。结合GaAs光导开关,开展了固态Blumlein脉冲形成线实验研究工作,在脉冲充电电压约25kV的条件下,固态Blumlein脉冲形成线实现脉冲电压输出约23kV。     

Development of accelerator mass spectrometry assisted by isotope-selective laser photodetachment for monitoring 129I

A prototype system was developed to investigate an isotope-selective laser photodetachment technique for a ¹²⁹I accelerator mass spectrometer. A pulsed ion source for negative iodine ions (I⁻) that employed laser ablation proved to be suitable for isotope-selective laser photodetachment. Laser photodetachment of pulsed negative iodine ions was estimated to have an efficiency of about 81% based on a model calculation for the prototype system with a tunable pulsed Ti:sapphire laser.     

Local environment of Te in GaTe and Ga2Te3 studied with119Sn and129I Mössbauer spectroscopy

The compounds GaTe and Ga₂Te₃ have been studied with Mössbauer source spectroscopy, using the decays^119mTe→¹¹⁹Sb→¹¹⁹Sn and^129mTe→¹²⁹I. For Ga₂Te₃, which has a defect zincblende structure, the spectra give satisfactory fits using two components with intensity ratio roughly 2∶1, in agreement with the two crystallographic sites in this compound. The Mössbauer spectra of GaTe are not easily understood in terms of the three inequivalent Te sites present in this compound. The relevance of these results for the interpretation of Mössbauer spectra observed after high-dose Te implantation in GaAs is discussed.     

An apparatus for NMR of laser polarized 129Xe on single crystal surfaces

Due to a lack of at least 2 orders of magnitude in the amount of sample nuclei, single crystal surfaces are out of reach for conventional NMR measurements. Our aim is to prove that highly polarized ¹²⁹Xe provides a technique to overcome this restriction. Therefore an apparatus for polarizing ¹²⁹Xe up to 0.7 by spin transfer from optically pumped Rb has been designed as well as an NMR spectrometer in combination with a UHV chamber with sample cleaning, cooling and characterization abilities and a special manifold of glass stopcocks with a liquid nitrogen cooled trap for dosing nitrogen free polarized Xe into the chamber onto the surface. This revised version was published online in August 2006 with corrections to the Cover Date.     

NaREO2 (RE= Lu，Y) 的制备及其结构的研究

用高温固相法制备了NaLuO2和NaYO2晶体粉体.制备纯相的NaLuO2粉体晶体困难,而制备纯相NaYO2粉体晶体相对容易.为了测定NaLuO2产物中含少量Lu2O3不纯相的量,用X射线衍射绝标法确定了样品中这两者的重量比和谱峰比的关系,得到了绝标法常数kLu2O3关键词： 2')" href="#">NaLuO2 2')" href="#">NaYO2 2O3')" href="#">Lu2O3 XRD定量分析 稀土发光     

Electronic conductivity of mechanochemically synthesized nanocrystalline Ag1−x Cu x I system using DC polarization technique

A study of electronic conductivity using the DC polarization technique has been carried out for AgI and Ag_1−x Cu _x I (where x=0.05, 0.15, 0.25) solid solutions over a range of temperatures from 300 K to 473 K. A diode-like current-voltage characteristics arises from microscopic p-n junctions an enhanced electronic conductivity of the order of 10⁻³A is observed for undoped AgI and Cu-doped AgI. Activation energies (E _a) for electronic conductivity obtained from log σ (Ω⁻¹ cm⁻¹) vs. 1000/T (K⁻¹) were 0.48, 0.6, 0.74 and 1.01 eV for AgI, Ag_0.95Cu_0.05I, Ag_0.85Cu_0.15I and Ag_0.75Cu_0.25I solid solutions respectively. The near-twofold increase in activation energy (1.01 eV) observed upon 25% Cu doping is due to the substantial concentration of current carriers/holes injected by Cu while replacing Ag⁺ in AgI. Based in part on the paper presented at first National Conference on Nanoscience and Technology, National Chemical Laboratory, Pune, 7–8 March 2005.     

Relation between surface structures and sputtering ratios of copper single crystals

Polished (100) Cu crystals have been bombarded at target temperatures of 204 K, 294 K and 456 K by 10 and 20 keV Ne⁺ ions up to a total dose of 1.7 × 10¹⁹ ions/cm². The plane of incidence was chosen to be a {100} plane perpendicular to the surface. Measurements have been performed for incident angles between 36° and 44° with respect to the surface normal. In this angular interval the sputtering ratio and the surface structure have been studied by weightloss and replica electron microscope techniques respectively. At target temperatures of 204 K and 294 K an anomaly was observed in the curve of the sputtering ratio versus angle of incidence. A small peak appears where the curve slopes towards the 〈110〉 minimum. The position and height of the peak is a function of target temperature and ion energy.

This sputtering submaximum is accompanied by the formation of {100} orientated furrows perpendicular to the ion beam. The nucleation of this relief is tentatively discussed in terms of local deviations from perfection of the surface, which might be due to a singularity in the production of focusing collisions influencing the damage structure. The growth of the furrows and the submaximum in the sputtering ratio are discussed in terms of the angle between the ion beam and the characteristic {110} side of the furrows.

These sputtering and faceting phenomena have not been observed at 20 keV Ar⁺ ion bombardment nor generally under bombardment at a target temperature of 456 K.     

Cross-section measurement for the ~(93)Nb(n,2n)~(92g)Nb reaction at the neutron energy of 14.6 MeV by the AMS method

The cross-section for the~(93)Nb(n,2n)~(92g)Nb reaction has been measured at the neutron energy of 14.6 Me V using neutron activation and accelerator mass spectrometry(AMS)determination of the long-lived product nuclide~(92g)Nb.The neutron energy was generated from the D+T neutron source at the China Institute of Atomic Energy(CIAE).The neutron flux was monitored by measuring the activity of~(92m)Nb produced in the competing reaction channel of~(93)Nb(n,2n)~(92m)Nb.At the neutron energy of 14.6 MeV,the~(93)Nb(n,2n)~(92g)Nb reaction cross-section of(736±220)mb was obtained for the first time.     

Interaction Products of 12·5 Deuterons with Molybdenum and their Isolation Possibilities from Worn-out Cyclotron Parts

Using chemical separations and radiometric measurements medium-half-life irradiation products of molybdenum with 12.5 MeV deuterons were determined (⁹⁰Nb, ⁹²Nb, ^95mNb, ⁹⁵Nb, ⁹⁶Nb, ⁹⁹Mo, ^95mTc, ⁹⁶Tc, ^99mTc) as well as thick target yields for some of them: ⁹²Nb (0.22 μCi/μAh), ⁹⁵Nb(0.05 μCi/μAh), ⁹⁹Mo (64 μCi/μAh), ^95mTc(0.76 μCi/μAh), ⁹⁶Tc((62.5 μCi/μAh). Moreover isolation possibiities of radioactive preparations from removed worn-cut molybdenum parts of the U-120 cycletron are discussed.     

129I-Mössbauer spectroscopic study of iodide-containing chalcogenide glasses

¹²⁹I-Mössbauer spectroscopy was used to study the short-range order in I-containing chalcogenide glasses. It was found that AsXI glasses, where X=S or Se, are molecular solids composed from molecular units of arsenic iodide and arsenic chalcogenide. The local environment of iodide ions in ternary superionic conducting glasses AgI?Ag₂S?As₂S₃ is similar to that in the crystalline superionic conductor Ag₃SI and differs distinctly from iodide local order in binary vitreous alloys AgI?As₂S₃ and crystalline AgI.¹²⁹I-Mössbauer spectra of all glasses were fitted satisfactory, when a distribution of the electric-quadrupole coupling constant is taken into account.