Materials applications of nuclear microprobes

This is a review of the use of nuclear microprobes in support of a wide variety of “ materials” sciences. Applications areas covered include metallurgy, solid-state physics, fusion research and HT superconductors; some examples are described. The list of references concentrates on the substantial range of publications subsequent to reviews published in 1987.     

核探针技术的现状和发展

围绕近１０年来召开的五次国际会议，评述了核探针技术在显微分析和显微成像方面的发展概况，介绍了它们在生物、微电子、环境和考古领域中的应用状况。     

Ionoluminescence technique for nuclear microprobes

Ionoluminescence (IL) produced by MeV/amu particles in the Nuclear Microprobe carries rich information on the nature of the chemistry and physics in the various types of materials, such as the molecular structure and ion's valence, etc. IL/PIXE methods offer unique ways to study the general luminescence phenomenon by directly relating the trace element information provided by PIXE to IL spectroscopic results. The IL can also be used to identify the organic molecular structure, hence, the combination of the IL data with the PIXE elemental data provide a new tool for biology and medicine studies. One example is the epidermis from the human skin, which exhibits a clear IL. IL is very sensitive to the local chemical environment conditions of the excitation point, therefore, it can be very effective to study the beam modification and beam damage effects. The beam damage problem in the Nuclear Microprobe applications is discussed.     

Geochemical utilization of nuclear microprobes

Analysis of geological materials may be the most challenging application for nuclear microprobes. Quantitative multi-element PIXE results are required on thick, compositionally complex, fine-grained materials. Major elements such as calcium and iron dominate the spectra that include numerous X-ray peak overlaps from a wide range of minor and trace elements. A concerted effort is required to optimize sample selection, data acquisition, and data reduction. Geochemical complexities can also make RBS and nuclear reaction analysis difficult.At Los Alamos, we are rebuilding our superconducting-solenoid nuclear microprobe beam line. We have moved to a new 3 MV tandem accelerator, simplified our ion optics, added two-dimensional beam scanning, and are working on a new precision stage and vacuum chamber. Continuing development of our software is aimed at obtaining maximum compositional information from PIXE spectra.In addition to the geochemical work of Cahill (UCD), Cabri (Ottawa), Clayton (Lucas Heights), and Minkin (USGS/Heidelberg), we (and our collaborators) have addressed several meteoritic and terrestrial problems. These range from early solar system condensation, planetary differentiation, and the possibility of “martian” meteorites, to in-situ retorting of oil shale, mid-ocean ridge hydrothermal processes, and the deduction of American indian trade routes through the characterization of the source minerals used in their copper metallurgy.Natural and synthetic standards have demonstrated that PIXE spectra can yield quantitative concentrations for more than 60 elements in a single spectrum and that, in favorable cases and with effort, sub-ppm detection limits are attainable.     

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.     

加速器质谱与环境科学

介绍了近年来国内外用加速器质谱计在环境科学方面的研究工作,包括测量城市空气污染、监测来自核设施的泄漏和有关全球环境的测定。为了适应多学科应用研究的需要,经过对装置进行大规模的改造和对高精度14^C测年方法的研究,北京大学加速器质谱计^14C测量精度已经达到好于0．5％的水平。在国家重大项目“夏商周断工程”中,测定了大量样品并结合考古已经达到好于0．5％的水平。在国家重大项目“夏商周断代工程”中,测定了大量样品并结合考古信息给出了比较可靠的年表。     

Applications of proton and nuclear microprobes in ore deposit mineralogy and metallurgy

The micro-PIXE technique usefully complements the analytical capabilities of the electron microprobe in many investigations of ore deposit mineralogy and metallurgy. Unfortunately, micro-PIXE has not been widely used, largely because of a paucity of accessible proton/nuclear microprobes designed with sample- and data-handling facilities suitable for mineralogical targets.Ore deposit mineralogy studies are performed to achieve a wide range of objectives: from the identification of parameters useful for mineral exploration through an understanding of the genesis of ore deposits to a complete characterization of the minerals, necessary to provide guidance for mineral beneficiation and metal extraction. Trace-element information, to calculate partition coefficients between co-existing minerals, or on fluid inclusions, provides geothermometric data on ore deposits. Dating of mineral deposits can be done by measuring the trace quantities of U, Th and Pb in zircon crystals. Efficient metal extraction depends on knowledge of the mineralogical distribution of elements of economic interest (e.g., Ag, Au, Pt-group) as well as knowledge of those which can contaminate the environment or the efficiency of metallurgical processes (e.g., Se, As).The specific requirements for an ideal proton microprobe for mineral analyses are discussed. In addition, new analytical data are presented for sulphide minerals (troilite and pentlandite), an oxide mineral (chromite), and for copper anodes.     

Silicon counters for nuclear spectrometry

Laboratory models of surface-barrier and diffusion-type silicon n-p counters were developed which were suitable for nuclear spectrometry. The counters have linear pulse height-energy dependence for particles with 60 paths (in particular, for -particles with energies up to 10 Mev), and 0.5 % resolution for an E of 5.5 Mev (with units of small area).The authors consider it a pleasure to thank engineer G. V. Khozov, technicians I. A. Lebedeva and G. D. Gusarina, and machinist P. I. Gorshkov for helping greatly in this work.     

Accelerator mass spectrometry with time-of-flight measurement

A time-of-flight detection system for the measurement of microscopic concentrations of long-lived radioisotopes has been set up at the Munich MP tandem accelerator. The technique allows an unambiguous mass determination for heavy ions up to the actinides. As a first test of the system, the concentration of ¹²⁹I in iodine has been measured for several samples of mineral and biological origin. The smallest ¹²⁹I/¹²⁷I ratios measured were a few times 10⁻¹³. The high sensitivity of the method was achieved by using a 90° injector with a good mass resolution, a special technique of stabilizing the terminal voltage with an auxiliary beam, and a time-of-flight system with a mass resolution of 800.     

High energy ion microprobes for surface analysis

Ion beam analytical techniques can be used in an ion microprobe for any kind of in situ analysis. These techniques are compared with other microprobes with respect to resolution sensitivity, and analytical depth. A variety of microscopic methods is in use for obtaining structural information in connection with the analysis. Although normally the analyses will be nondestructive, problems with radiation damage and heating may occur. Since vacuum is not a mandatory requirement some unique analytical possibilities are offered by the high energy ion microprobes.     

基于扫描核探针技术的大气气溶胶单颗粒物源识别与解析方法研究与应用

将高分辨、高灵敏的扫描核探针(SNM)技术与人工神经网络(ANN)模式识别方法相结合,以单个气溶胶颗粒物化学表征为基础,开展大气气溶胶源识别与解析的新方法研究。摸索出单颗粒气溶胶SNM靶样的制备方法。建立了SNM多站多参量分析模式的数据获取系统和分析条件。用SNM测定了单个大气气溶胶粒子的元素谱特征。基于标准的误差反向传输神经网络算法,建立ANN模式识别系统,直接对单个气溶胶粒子的SNM分析能谱模式进行识别,判别其来源,计算源的贡献率。将建立的方法初步应用于上海市大气PM10源识别与解析研究。结果表明该方法解析能力强,解析结果客观,具有查找未知污染源、解析低浓度污染源的特点。     

Accelerator mass spectrometry

The general principles of accelerator mass spectrometry, together with recent progress in the subject, are discussed.     

Fe-Cr-V ferritic steels for possible nuclear applications

Basic mechanical and metallurgical properties of specific ferritic Fe-Cr-V alloys and steels with 5, 10, and 15 wt.% vanadium were investigated. Vanadium is an effective carbide former and can also form a brittle sigma phase with chromium. Therefore, the microstructural investigations focused on the determination and analysis of possible precipitations. The present study showed that sigma phase precipitates increase significantly in alloys with 10 wt.% Cr and 10 wt.% V. The addition of carbon led to grain refinement due to the stabilizing effect of VC. In this way, precipitation hardening as well as fine grain strengthening could be quantified for this class of material. However, compared to typical martensitic steels, the strength of the considered ternary Fe-Cr-V alloys and steels is still lower.     

Pipe whip analysis for nuclear reactor applications

The main problems encountered in pipe whip analysis are discussed and the way the authors tried to solve them is described. Such problems are:

1. (a) Breakage locations: AEC criteria are presented and discussed.

2. (b) Force computations: The jet force intensities during the accident are computed following Moody's theory. A computer program makes such an analysis automatically. Forces consequent to a longitudinal and a circumferential break are calculated; The forces consequent to the longitudinal break are computed as a sum of the forces consequent to two circumferential breaks, a mitigation coefficient is assumed.

3. (c) Preliminary analysis: Provided that a ‘restraint solution’ is necessary (and the related criteria are briefly discussed), a tentative distribution of the restraints is computed by means of a simple energy balance between the work done by the jet forces and the work absorbed both in the pipe and the restraint. A computer program makes such an analysis automatically.

4. (d) Final solution appraisal: The tentative solution obtained in the initial step is re-evaluated by means of a detailed dynamic elastoplastic code (FRUSTA, which is described in the companion paper).

A typical example is given, the jet forces and a tentative restraint distribution are computed; the various models used in the final appraisal solution are described and the results are evaluated mainly in order to check the validity of the preliminary criterion.     

Prospects for applications of ship-propulsion nuclear reactors

Special Design Office for Machines. Translated from Atomnaya énergiya, Vol. 76, No. 4, pp. 318–326, April, 1994.     

Enhanced computer reliability for nuclear power applications

Reactor operator assistance and augmentation by on-line digital computers will improve power reactor safety. To function in this expanded role, the computers must be both extremely reliable and failsafe. Topics in computer and software reliability are discussed, and it is pointed out that all of these error-extinguishing characteristics are available today in general-purpose equipment built for the military. Tactical military computers, peripheral equipment, and high-order languages have the refinements necessary for safety-related reactor control room operations.     

Isotope dilution inductively coupled plasma mass spectrometry for determination of 126Sn content in spent nuclear fuel sample

The ¹²⁶Sn content in a spent nuclear fuel solution was determined by isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) for its inventory estimation in high-level radioactive waste. A well-characterized irradiated UO₂ fuel sample dissolved in a hot cell was used as a sample to evaluate the reliability of the methodology. Prior to the ICP-MS measurement, Sn was separated from Te (¹²⁶Te), which causes major isobaric interference in the determination of ¹²⁶Sn content, along with highly radioactive coexisting elements, such as Sr (⁹⁰Sr), Y (⁹⁰Y), Cs (¹³⁷Cs) and Ba (^137m Ba), using an anion-exchange column. The absence of counts attributed to Te at m/z = 125, 128, and 130 in the Sn-containing effluent (Sn fraction) indicates that Te was completely removed from the anion-exchange column. After washing, Sn retained on the column was readily eluted with 1 M HNO₃ accompanied with approximately 80% of the Cd and 0.03% of the U in the initial sample. Owing to the presences of Cd and U in Sn fraction, the measurements of ¹¹⁶Sn and ¹¹⁹Sn were affected by the isobaric ¹¹⁶Cd and the doubly charged ²³⁸U²⁺ion, resulting in the positive bias of the determined values. With the exception of the isotopic ratios including ¹¹⁶Sn and ¹¹⁹Sn, ¹¹⁷Sn/¹²⁶Sn, ¹¹⁸Sn/¹²⁶Sn, ¹²⁰Sn/¹²⁶Sn, ¹²²Sn/¹²⁶Sn and ¹²⁴Sn/¹²⁶Sn were successfully determined and showed good agreement with those obtained through ORIGEN2 calculations. The measured concentration of ¹²⁶Sn in the spent nuclear fuel sample solution was 0.74 ± 0.14 ng/g, which corresponds to 23.0 ± 4.5 ng per gram of the irradiated UO₂ fuel (excluding the presence of ¹²⁶Sn in the insoluble residue). The results reported in this paper are the first experimental values of ¹²⁶Sn content and isotope ratios in the spent nuclear fuel solution originating in spent nuclear fuel irradiated at a nuclear power plant in Japan.     

U measurement with accelerator mass spectrometry at CIAE

²³⁶U is a long-lived radioactive isotope which is produced principally by thermal neutron capture on ²³⁵U. ²³⁶U may be potentially applied in geological research and nuclear safeguards. Accelerator mass spectrometry is presently the most sensitive technique for the measurement of ²³⁶U and a measurement method for long-lived heavy ion ²³⁶U has been developed. The set-up uses a dedicated injector and the newly proposed ²⁰⁸Pb¹⁶ molecular ions for the simulation of ²³⁶U ion transport. A sensitivity of lower than 10⁻¹⁰ has been achieved for the isotopic ratio ²³⁶U/²³⁸U in present work.