用低本底γ谱仪测定宁强陨石宇宙成因放射性核素

本文介绍利用塑料闪烁体反符合屏蔽低本底NaI(T1)γ谱仪对我国第一块碳质球粒陨石——宁强陨石中的~(22)Na、~(26)Al、~(40)K、~(54)Mn和~(60)Co作非破坏分析,并进行数据处理。结果表明,所用的方法基本上是成功的。谱仪以符合方式工作时,对~(60)Co的探测灵敏度为7.4dpm/kg,最低可探测限为14dpm/kg。     

High Spin States in A≈50 Region

The present experiment was carried out at HI-13 tandem accelerator of the China Institute of AtomicEnergy in Beijing. High spin states in ~(52)Mn, ~(53)Mn and ~(54)Mn were populated via ~(12)C ~(48)Ti fusionevaporation reactions at beam energy of 55～85 MeV. The target was a ~(48)Ti foil with a thickness of 1.5mg/cm~2, backed with a lead layer of about 20mg/cm~2 to stop the recoils. Gamma-gamma coincidentevents were recorded with an array consisting of fourteen Compton suppressed HPGe-BGO spectrometers.     

中子活化分析法测定吉林陨石中微量镓

陨石中的Na、Mn等杂质元素,经中子活化后产生~(24)Na和~(56)Mn等核素,它们干扰Ga的测定,因此必须进行放化分离。实验步骤如下: 称取20mg陨石样品置于铝制照射筒中,与标准一起在中子通量约为1×10~(13)n·cm~(-2)·s~(-1)的反应堆中照射20小时,冷却1天后将样品置于高压溶样埚中(高压溶样埚中已置有200μg镓载体),加1ml浓HNO_3、5ml浓HF,摇匀后置于烘箱中烘2小时,温度180～200℃。取出后在冷水中冷却15分钟,再打开高压溶样埚,将溶液转入白金坩埚中,分别加2次1ml HClO_4,置于电炉上缓慢加热挥发除去SiF_4和HF,加热至近干,加1.5ml浓HCl,则生成清澈的黄色溶液,再加热至近干,然后用3ml 7N HCl清洗白金坩埚,转     

用放射化学中子活化方法研究陨石中的Os和Ru同位素丰度

选择南丹、邕宁铁陨石经2mol/l H_2SO_4处理后的残渣,和吉林、洮南石陨石的金属相部分,以Os、Ru试剂(地球同位素丰度)为标准,用放射化学中子活化方法测定~(190)Os/~(184)Os及~(96)Ru/~(102)Ru的比值。实验全面考虑了在照射、分离、测量过程中各种因素对Os和Ru同位素丰度测定的影响。对~(190)Os/~(184)Os的测量统计误差可控制在1％以内。实验结果表明,这4种陨石的~(190)Os/~(184)Os和~(96)Ru/~(102)Ru的比值与地球标准相比,不存在统计上有意义的同位素丰度比异常。     

质子活化分析吉林陨石中痕量硼

陨石中痕量硼的分析可以为陨石成因研究提供必要的数据。以前对陨石中硼含量分析均采用比色法和光谱分析法。由于许多玻璃器皿都有很高的含硼量,因此测定中沾污是一个严重的问题。用质子活化分析法测定硼,灵敏度高,没有沾污干扰。用该法测定超纯硅中痕量硼,灵敏度可达10~(-8)％。采用质子活化分析法测定吉林陨石中硼含量,用燃烧法作快速放化分离;采用γ-γ符合测量;利用~(11)B(p,n)~(11)C核反应,并引入平     

The Calculations of ~(56)Fe(n,x)~(51)Cr,~(52,54,56)Mn Reactions Cross Sections up to 60 MeV

A set of neutron optical potential parameters for ~(56)Fe in energies of 4～100 MeV was obtained by fitting available experimental data. The yield cross sections of the activation isotopes ~(51)Cr, ~(52)Mn, ~(54)Mn, and ~(56)Mn in n ~(56)Fe reaction are calculated and predicted in energy range up to 60 MeV.     

用裂变径迹法研究吉林陨石中的铀分布

众所周知,陨石中的铀含量是很低的。要想了解陨石中不同矿物相和不同结构内的铀分布,用一般的放射性测量方法或核乳胶方法难以达到目的。但用裂变径迹法可以得到微量铀的显微分布图。其优点是需要的样品很少,灵敏度可高达10~(-11)g/g。 将吉林陨石样品磨制成面积约0.3×0.3cm~2的光薄片,厚度大于30μm。把Lexan(聚碳酸脂)切成大     

~(56)Fe(n,p)~(56)Mn反应截面的测量

在E_n=12.8—18.2兆电子伏能区,用活化法测量了~(56)Fe(n,p)~(56)Mn反应截面,在E_n=14.63±0.20兆电子伏处做了绝对测量,结果为108.0±2.9毫靶。中子通量用伴随粒子法测定。对T(d,n)~4He反应的中子角分布也作了测定。~(56)Mn的放射性用φ10×7.6厘米的Nal(Tl)闪烁谱仪测量,~(56)Mn特征γ射线的探测效率用4πβ-γ符合法测定的~(56)Mn标准源刻度。本文还对用伴随粒子法测量中子通量作了较详细的叙述。测量结果同国外数据作了比较,并做了简短讨论。     

利比亚玻璃陨石的活化分析和东北“玻璃陨石”类似物的检验

本工作分析了利比亚玻璃陨石,并检验了我国东北“玻璃陨石”类似物,结果如表所示。并得到:(1)利比亚玻璃陨石是一种高SiO_2含量的玻璃陨石,稀土元素含量和世界上四大散落区玻璃陨石有较大差别。(2)利比亚玻璃陨石1~#、2~#和中国琼雷地区玻璃陨石的稀土元素相对含量的模式图的不同,反映了它们来自不同的母岩。(3)两颗东北玻璃陨石类似物的外形、     

Theoretical Calculation of n ~(59)Co Reaction in Energy Region up to 100 MeV

A set of neutron optical potential parameters for ~(59)Co in energy region of 2～100 MeV was obtained based on concerned experimental data. Various cross sections of n ~(59)Co reactions were calculated and predicted. The calculated results show that the activation products ~(58,57)Co, ~(59)Fe, and ~(56)Mn are main neutron monitor reaction products for n ~(59)Co reaction in energy range up to 100 MeV. ~(54)Mn production reaction can be a promising neutron monitor reaction in the energy region from 30 to 100 MeV.     

Manganese-53: Development of the AMS technique for exposure-age dating applications

The cosmogenic isotope ⁵³Mn is produced by spallation of iron in surface rocks. The long half life of this isotope makes it attractive for use in erosion rate studies in slowly eroding landscapes such as Australia. We describe the development of AMS methods for detection of ⁵³Mn using the 14UD accelerator at the Australian National University. The first step of this development involved the production of ⁵³Mn using a heavy-ion fusion–evaporation reaction to make test standards. Then, the chemistry protocol for isolating ⁵³Mn and reducing the Cr levels, of which ⁵³Cr is a serious interfering isobar, was developed. Lastly we employed a gas-filled magnet which was used to discriminate ⁵³Mn from the intense ⁵³Cr background.     

Highly sensitive AMS measurements of 53Mn

Our AMS system, with the gas-filled detector system GAMS, has been optimized for measurements with ⁵³Mn. A high sensitivity has been achieved. A newly installed cesium sputter ion source yields an improved emittance, and thus a higher mass resolution. By the extraction of the manganese molecule MnF^? instead of MnO^? we can suppress the isobaric chromium background in the ion source by more than a factor of three. The GAMS system achieves an isobaric suppression factor of about 3 × 10⁸. Measurements on blank samples yielded upper limits for the ⁵³Mn/⁵⁵Mn ratios of 7 × 10^?15.     

Isobaric identification techniques of AMS at CIAE

Some long-lived nuclides, such as ³⁶Cl, ⁴¹Ca, ⁵³Mn, ⁷⁹Se, etc., are very interested in life science, environment science, geo- and cosmo-sciences, nuclear wastes management, and other fields. Taking the advantages in high sensitivity and the strong ability to reduce the interferences from molecular ions and isobars, AMS has been one of the most promising methods for the measurement of these nuclides. However, the sensitivity of AMS is often unsatisfactory due to the interferences of stable isobars especially for medium and heavy radioisotopes. Gas-filled time of flight (GF-TOF), Gas-filled Magnet with a time of flight (GFM-TOF), Bragg Curve detector and energy loss (ΔE) combined with a Q3D magnetic spectrometer (ΔE-Q3D) are among the techniques used or being developed in AMS lab of China Institute of Atomic Energy, in an attempt to further reduce the interferences from isobars. These techniques will be tested in our AMS measurement of ⁵³Mn, ⁷⁹Se, ⁹³Zr, ⁹⁹Tc, etc., for identifying isobaric interferences.     

The thermal-neutron absorption cross-sections of Mn and S

In a recent note a new value for the thermal-neutron capture cross-section of Mn was reported with significantly reduced uncertainty. The value was based on ratios of the cross-sections of H and Mn measured by Mn-bath dilution techniques. Recent measurements of the absorption cross-section of S, and of its ratio to that of H permit a simultaneous evaluation of the thermal-neutron cross-sections of H, S and Mn. The Mn cross-section remains unchanged at 13.41 barn, and a value of 535 ± 6 mbarn is recommended for S.     

Elemental analysis of edible grains by micro-PIXE: Common buckwheat case study

The aim of this study was the adaptation of the micro-PIXE method for analysis of nutritionally relevant heavy elements in different tissues of the grain of common buckwheat (Fagopyrum esculentum), as a representative nutritionally interesting grain food source. At 57% of the buckwheat grain biomass, the endosperm was a modest nutrient source when compared to the cotyledons, at 17% of the biomass. These latter contained high concentrations of trace elements, representing 91% of the total grain Zn, 87% for P, 70% for S, 62% for Mg, 60% for K, 54% for Cu, 53% for Mn and 35% for Fe. The husk provided storage for 85% of the total Ca, 84% for Al, 83% for Si, 76% for Cl, 69% for Ti and 46% for Fe. Knowledge on these preferential elemental constitutions of the different grain tissues makes the possibility of designing target products with nutritionally optimal constitution more feasible. These data represent a basis for a more targeted approach to nutritional improvement of grains intended for human consumption.     

Spallogenic nuclides in meteorites by conventional and accelerator mass spectrometry

Light noble gases and ¹⁰Be were determined in 15 ordinary chondrites by conventional mass spectrometry and accelerator mass spectrometry, respectively. Aliquots of these samples had previously been studied for ²⁶Al and ⁵³Mn. Be was extracted from 10–20 mg of meteorite and ¹⁰Be was determined by means of the 6 MV tandem Van de Graaff accelerator at ETH-Zürich with a reproducibility better than 3%. A detection limit of 0.7 dpm/kg meteorite was achieved. Based on the noble gas data a ¹⁰Be production rate of 17.8 ±0.4 dpm/kg was established for chondrites with H-group chemistry. Short exposure ages of meteorites were determined via the ¹⁰ Be concentrations. A slight correlation of ¹⁰Be production rates with shielding could be observed. During the last 4 million years the long-term averaged cosmic ray intensity did not vary by more than 30%.     

基于AKMC方法研究Mn对Cu团簇析出的影响

Cu团簇析出是影响FeCu合金体系安全服役的主要因素之一。本文基于原子动力学蒙特卡罗（AKMC）方法研究了热老化条件下,合金元素Mn对Fe-1.34at.%Cu-Xat.%Mn（X为0、0.27、1.2、3、5）合金中Cu团簇析出的影响。研究结果表明,随着体系中Mn含量的增加,析出形核的纳米级Cu团簇的数密度不断增加;Mn含量对形核Cu团簇的平均尺寸影响不大。团簇中主要成分为Cu;团簇中Mn含量随初始基体中Mn含量的增加而增加。合金元素的成团参与百分比决定了团簇平均尺寸。Cu-Vac复合体较强的扩散能力及其较远的扩散距离是造成Cu团簇析出的主要因素;而Mn的加入会抑制Cu-Vac复合体的可移动距离和可移动能力,从而提高Cu团簇的数密度。合金元素Mn的加入会影响形核Cu团簇的尺寸、数密度,从而影响Cu团簇引起的硬化效应。     

Mn DEPLETION IN THE SURFACE LAYER OF STAINLESS STEEL 304 LN AT THE TEMPERATURE 1200 K

The Mn component of stainless steel 304 LN has been found to be severely depleted in the surface layer during heating at the temperature 1200 K. The surface concentrations of Mn were reduced by about 2- 3 orders of magnitude in comparison with the bulk value, as was revealed by a secondary ion mass spectroscopy (SIMS) system. And the Mn concentration gradient in the surface layer was examined, too, by SIMS. Massive preferential losses of Mn have been determined by using the catcher technique and proton induced X- ray emission (PIXE). A theoretical model has been proposed for calculating the surface concentration changes for a component in an alloy under heating. A comparison shows a good agreement between the calculation and experimental results from SIMS and catcher technique.     

上海市青少年外周血四种成分的多元素状况研究

应用“percoll”液对上海市53名大、中学生外周血的血浆、血小板、单核淋巴细胞及红细胞进行分离后,对四种成分中的20种元素进行了测定分析,除Se采用F-78型脉冲极谱仪分析外,其它元素均采用ICAP-9000型等离子体直读光谱仪测定。结果发现:(1)在不同年龄组中,大学生组血浆Mo、Se以及单核淋巴细胞中Fe、Zn、Ca、Cu、Ni含量高于中学生组,而血浆Mn则低于中学生组;(2)在不同性别的人群间,中学生组人群中血浆Ca、Cr含量男性高于女性;大学生组红细胞中P、Fe两元素的含量为男性高于女性,而单核淋巴细胞中除Ti、Si、Cd、Co外,其余Zn、Cu、Fe等16种元素含量均为女性高于男性;(3)单核淋巴细胞中元素含量高于血小板及红细胞中元素含量;(4)血小板中元素含量无性别、年龄差异;(5)血液各成分中元素存在一定相关关系。     

EXAFS and SR-XRD study on Mn occupations in Zn1−xMnxO diluted magnetic semiconductors

Mn-doped ZnO films were prepared by radio frequency (RF) magnetron sputtering on sapphire substrate. Mn content was determined by proton induced X-ray emission (PIXE). Only Mn, no other magnetic impurities such as Fe, Co and Ni were observed. Also, no precipitates such as MnO, Mn₃O₄ and other secondary phases or Mn clusters, were found by SR-XRD, even in Mn-doped content up to 11 at.%. EXAFS analyses showed that Mn atoms were incorporated into ZnO crystal lattice by occupying the sites of zinc atoms.