Introducing to XRF application

X-ray; Fluorescence Microbeam X-ray Fluorescence (MXRF); Multifunction Instruments; Micro-Nano Analysis (μ/n-XRF); Micro-Nano Analysis (μ/m-XRF)

Summary

The technical characteristics, instrument configuration, application fields and working range of X-ray fluorescence (XRF) analysis and microbeam X-ray fluorescence (MXRF) analysis are briefly described. The microbeam X-ray fluorescence instrument in China is reviewed from four types of instruments: collimated microbeam X-ray fluorescence, combined bulk X-ray fluorescence and microbeam X-ray fluorescence, spectrum/energy spectrum multifunctional combination and capillary X-ray converging lens microbeam X-ray fluorescence instrument. Application and development of radio fluorescence instruments and analytical techniques. The development of microbeam X-ray fluorescence technology is prospected from two aspects of analysis function positioning and technology development. It is proposed to further distinguish the traditional microbeam in situ (micro-field) XRF (MXRF) analysis in XRF analysis into “micro” nano-field analysis (μ/n-XRF)” and “micro-nano-field analysis (u/m-XRF)” )”, thus distinguishing the technology and the scope of application positioning is beneficial to the development of both in situ analysis technologies, especially the positioning also clearly explains the development and application of the function and scope of application of the integrated/micro-area combined instrument. The author emphasizes : In-situ (micro-area) analysis is not just for simple analysis work, but more importantly, the research on the characteristics of the tested sample and the interpretation of the results! The close cooperation between analysts and professional scientists can give full play to the in-situ micro-area analysis technology. Efficiency, fully interpret and demonstrate the scientific significance of the analysis results.

Introduction

It is well known that X-ray fluorescence analysis (XRF) is one of the most important analytical techniques in the field of inorganic elemental analysis today. As far as the entire analysis technology system is concerned, it is an overall analysis technology, and its analysis object is a macro sample, generally in the order of grams, and the scale above centimeters must be prepared into a uniform sample before analysis. The results of its analysis represent the average content of elements in the sample.

Micro-nano area analysis (μ/m-XRF) in microbeam X-ray fluorescence analysis (MXRF) is a new field of XRF analysis technology development, which belongs to the micro-nano area in situ (micro area) analysis in the entire analysis technology system technology, which analyzes the scale of the original sample or this tiny area in the original sample from 0.XX millimeters to centimeters. This technique has become an important means for the study of element content and distribution in tiny original samples or tiny regions of large samples. In recent years, with the development of X-ray light guide and polycapillary lens technology, microbeam X-ray fluorescence technology and its application have become an important direction and new hot spot in the development of XRF technology.

As early as the late 1950s and early 1960s, there were reports on the design of X-ray fluorescence analysis instruments for elemental analysis of small areas. The 35th (1986) International Conference on X-ray Spectroscopic Analysis reported such microbeam X-ray fluorescence analysis technology (MXRF) in more detail and attracted international attention. In recent years, with the development of X-ray tube and polycapillary lens technology and the growing demand for information on element content and regional distribution of tiny samples, MXRF analysis technology has developed rapidly, and its applications have become more and more extensive, becoming a new hot spot in the development and application of XRF technology.

The MXRF analysis device and instrument is mainly composed of a micro-beam X-ray source, a movable (rotating or XY moving) sample chamber of the sample stage, a detector and a computer system with the functions of complete machine control and data processing. According to the type of microbeam X-ray source, MXRF devices and instruments can be roughly divided into: collimated beam X-ray source and light pipe, polycapillary lens focusing X-ray source and other instruments.

(1) Collimated beam MXRF instrument: The device is relatively simple. Generally, the micro-beam X-ray is directly obtained by the X-ray tube and the collimating diaphragm, and the beam spot is at the level of 0.1 ~ 1mm. device development process.
(2) X-ray light guide, polycapillary lens MXRF instrument:
Since the mid-1980s, with the development of “duct X-ray optics” and the focused X-ray optical system based on it – X-ray lens (former Soviet scientists Kumarhof invention) and the development of a variety of X-ray optical components have caused a major change in X-ray control technology, providing a variety of simple, safe and efficient options for the wider application of X-rays, especially for building and It provides an important foundation for the development of various laboratory-type microbeam X-ray fluorescence instruments and devices.

1. Development and application of MXRF analysis technology in China

1.1 Collimated Microbeam XRF Instruments and Applications

Zhu Jieqing and Le Safety Group of Shanghai Institute of Nuclear Research, Chinese Academy of Sciences have been developing and applying XRF instruments with micro-beam spots since the late 1980s. They obtained 0.1mm X-ray beam spots by collimating, and scanned and analyzed the micro-beams of 1mm×1mm. manganese sulfide ore in the region, and two-dimensional contour distribution maps of multiple elements were obtained. Subsequently, the instrument has been gradually improved to form a series and introduced to the market.

In addition, the research team also developed a small-area X-ray fluorescence coating thickness gauge, which provides fast, convenient, safe, reliable, high-precision, Reproducible scientific testing method.

The cooperative research team of the Institute of High Energy Physics, Chinese Academy of Sciences and the National Geological Experiment and Testing Center used an MXRF device assembled with a high-power X-ray tube to scan and analyze the oceanic manganese nodules samples with a 0.1 mm microbeam spot, and obtained elements in the area of 40 mm × 45 mm. The two-dimensional distribution map has made technical preparations for the construction of the SR-μ-XRF experimental station in the Beijing Synchrotron Radiation Center. Although the spatial resolution of these instruments is mostly at the level of 0.05-1 mm, the beam spot of this size is more suitable for the element distribution analysis of tiny samples with the size of 0.05-XX mm, which is the application field with the most vigorous demand for MXRF in recent years. The micro-area element distribution of smaller-scale (sub-millimeter-sub-micron) substances is the research object of various micro-probe analysis techniques (micro-nano area analysis, μ/n-XRF) at the micron and sub-micron levels.

1.2 Integrated XRF and Microbeam XRF instruments and their applications

Since the mid-1990s, some Japanese companies (Shimadzu, Rigaku, etc.) have added MXRF devices to their wavelength dispersive X-ray fluorescence spectrometers (WDXRF). Micro-beam X-rays are obtained by using a collimated diaphragm, the beam spot size is 0.25-1 mm, and the scanning range is 0.XX-30 mm, and the line or surface scanning distribution map of the element can be obtained. The combination of bulk analysis and in situ (micro) analysis technology opens up new directions for XRF and MXRF matching applications. Although the spatial resolution level of microbeam is still in the sub-millimeter level, it has shown good development prospects in many practical applications. XRF) is difficult to solve these application problems.

Since the late 1990s, my country has successively introduced some wavelength dispersive X-ray spectrometers with micro-area analysis/distribution functions, including the XRF-1700 and XRF-1800 of Shimadzu Corporation of Japan, and the ZSX-100e and ZSX of Rigaku Corporation of Japan. Primus series, etc. Domestic users have carried out various research work using these instrument functions, and achieved remarkable results, and provided useful experience for the wide application of such instrument functions.

According to reports, Shimadzu has been developing this type of instrument since the mid-1990s. The beam spot is from 1 mm at the beginning to 250 μm later. It can perform fixed-point analysis, give quantitative analysis results, and obtain element distribution. Two-dimensional scanning images, thus making the wavelength dispersive X-ray fluorescence spectrometer a member of the broad family of generalized microanalysis instruments.

In the fields of metallurgy, geology, electronics, environmental protection, archaeology and material science, it is required to perform in-situ analysis in a sample area that can be discerned by the naked eye. The millimeter-level spatial resolution can not only accurately characterize the composition distribution of a small area of the sample, but also perform in situ analysis. Quantitative analysis, this is where the wavelength dispersive X-ray fluorescence spectrometer with the function of micro area analysis/element distribution analysis comes in. It has played an important role in geological and mineral resources, new material development, failure analysis, segregation determination of electronic products, metal materials, trace evidence of public security departments, and research on archaeological cultural relics, etc., and has expanded the application scope of single-function XRF.

The report also introduced the use of the instrument’s micro-area analysis function for qualitative identification of antimony, pyrite, turquoise, commemorative coins, etc., and quantitative analysis of small samples such as coins and archaeological relics. In terms of application, Wang Hequan et al. of Tsinghua University reported earlier that the XRF-1700 X-ray fluorescence spectrometer with surface scanning function of Shimadzu was used to determine the concentration of Ni in different crystal planes in Sr (NO3)2 crystals.

The micro-area analysis part of Rigaku ZSX Primus II has a positional resolution of 100 μm, and the minimum diameter of fixed-point analysis is 500 μm. Zhao Hongqiao et al. used Rigaku ZSX-100e X-ray fluorescence spectrometer to analyze the content distribution of 8 main ore-forming elements (Mn, Fe, Co, Cu, Si, Al, Ca and Ti) in the cobalt-rich crust thin-section samples, and obtained the results. Distribution characteristics of metallogenic elements in different growth ages.

Xu Benping applied the micro-area analysis function of ZSX-100e instrument to determine the content of oxide inclusions in steel. Liang Shuting’s group from Anhui Geological Experiment and Testing Center used the small area scanning function of Rigaku’s ZSX-100e X-ray fluorescence spectrometer to conduct a lot of research on geological applications as an important means of ore identification, and achieved a number of eye-catching results. The team also used this function to perform in-situ non-destructive testing of elements such as Ag, Cu, and Zn in silver alloys and jewelry, and obtain information on the distribution of chemical components at sample points, lines, or surfaces. A quantitative analysis method with good precision and accuracy was established.

1.3 MXRF and its applications in multifunctional XRF instruments

The CNX-808WE spectrum-energy spectrum composite X-ray fluorescence spectrometer led by the National Geological Experiment and Testing Center was successfully developed in 2017. The instrument has “two-spectrum combination, three functions” (spectrum, energy spectrum and element distribution analysis, and micro-area scanning (beam spot 1mm) comprehensive performance). The application research in the analysis of samples, etc., has realized a faster and non-destructive distribution analysis and research, and provided a strong technical support for the scientific research of geology, materials science, and environment.

In 2015, PANalytical launched a multifunctional XRF instrument, Zetium, which integrated functions such as spectrum, energy spectrum, and micro-area distribution analysis on one instrument. Small area scanning (beam spot 0.5mm) is combined with energy spectrum and wave spectrum, which shortens the scanning time, improves the analysis efficiency, and provides stronger technical support for the combined application of overall analysis and in-situ analysis technology. Yang Lihui of East China Normal University and others used the micro-area analysis function of this instrument to analyze the distribution of major elements inside the nodules from the core to the edge of the Quaternary laterite in Tongling, expanding the elements outside the qualitative and quantitative analysis function of the X-ray fluorescence instrument. The distribution function can accurately grasp the distribution of elements in each area of the sample, and explain some climate-related issues.

1.4 MXRF and application of X-ray condenser lens

In the 1990s, the scientific and technical personnel of the Institute of Low Energy Physics of Beijing Normal University carried out systematic research in this field, and achieved a series of important achievements in theory, device and application. Especially in the MXRF instrument and application with integral X-ray lens.

In 1992, the MXRF instrument was assembled with the X-ray lens of the composite capillary, the microbeam spot was 250 μm, and the sensitivity was increased by 10 times compared with the OMICRON microbeam fluorescence spectrometer without lens in the United States. When the integral X-ray lens was used in 1999, the beam spot of the MXRF system reached 50μm, which greatly improved the power density of the microbeam, and made the detection limit of elements such as Cr, Mn and Fe reach the order of 10-12.

In 2004, a wavelength dispersive MXRF spectrometer composed of a catheter X-ray lens and a position-sensitive proportional counter tube was reported to obtain high-intensity microbeam X-rays with a beam diameter of 50 μm, and the energy resolution of TiKa lines reached 4.4 eV, which is higher than Si semiconductor detectors are improved by 1 to 2 orders of magnitude. This is a new type of XRF spectrometer with high spatial resolution, high energy resolution and high sensitivity.

In recent years, the laboratory of the Institute of Low Energy Physics of Beijing Normal University has developed a three-dimensional confocal MXRF spectrometer composed of a capillary X-ray converging lens and an X-ray parallel beam lens. Nondestructive determination and spatial distribution analysis.

The device improves the power gain of the lens, reduces the dependence on high-power X-ray sources, reduces the background and improves the detection limit by three-dimensional confocal, which is another important development direction of MXRF technology. Combined with the research on X-ray beam forming devices and MXRF devices, the team has also carried out multi-field application research.

In 2007, Xu Xuelian et al reported that they designed a compact microbeam X-ray fluorescence spectrometer composed of a 50μm micro-focusing source from Germany RTW Company, an X-ray converging lens and an XR100CR Si-PIN semiconductor detector from Amptek Company in the United States. The line distribution scanning analysis of elements within 50mm of pine needles was carried out. Striking exploration and research has been carried out in archaeology, environment, atmospheric particulate matter, fingerprint extraction, physical evidence traceability, etc.

Chengdu University of Technology is another active team in the MXRF field. In 2010, an MXRF system consisting of a micro-beam X-ray source (spot 35 μm) composed of an X-ray tube and an X-ray focusing lens, a CCD camera for microscopic observation and positioning, and an electrically cooled Si-PIN semiconductor detector was reported ( IED-6000 X-ray fluorescence in-situ micro-analyzer), carried out micro-area multi-element qualitative and quantitative rapid analysis of rock minerals, the precision was better than 10% (RSD), and ore particles and atmospheric particles were detected and analyzed , and quantitative analysis and identification of minerals.

In 2017, Luo Liqiang and others of the National Geological Experiment and Testing Center developed a microbeam XRF instrument. The device uses a convergent capillary lens from the United States as a focused X-ray light source (spot 15μm). The instrument can analyze elements in the periodic table after potassium (K). , and used in biogeochemical research to reveal the tolerance mechanism of plant seeds to the retention of toxic elements in the roots.

The MXRF instruments introduced in domestic applications have also received extensive attention. After launching a series of energy dispersive (EDX) instruments with a measurement area of millimeters, Shimadzu developed a polycapillary micro-energy dispersive (μ-EDX) for micro-area analysis (measurement area of microns) in 2001. The series of instruments, with a spatial resolution of 50μm, can scan and analyze in a 40mm area. If a fluoroscopy counter is selected, it can also detect the internal structure of the sample. This series of instruments has 3 models: standard type (uEDX-1200, element range Al-U, WD6.5mm); light element high sensitivity type (μEDX-1300, element range Na-U, WD1.5mm) and high precision , Electric cooling type (μ-EDX-1400, element range Al-U, WD6.5mm)

MXRF has also been widely used in criminal investigation and forensic identification: Xu Che et al. used Eagle III microbeam X-ray fluorescence spectrometer (μ-EDXRF, beam spot 100 μm) of EDAX Company to carry out non-destructive inspection of laser printer handwriting, which provided scientific evidence for the identification of toner. in accordance with.

Sunlin Hu of the Department of Physics of Sun Yat-sen University and others used Eagle II μ-probe microbeam XRF from EDAX Company, Rh target X-ray tube and single capillary focusing optical system (spot 300 μm) to scan and analyze 225 pieces of real and fake banknotes that were dyed black. The element distribution characteristics of the black-dyed real and fake banknotes were identified, and the type of banknotes was identified. The test accuracy was 100%.

After that, the acid-resistant siliceous particles in the lungs were detected, and their surface content can be used as a drowning diagnostic indicator. . Guangzhou Institute of Criminal Science and Technology Li Qian et al. used Eagle II μ-probe microbeam XRF (capillary diameter 300 μm, 15 cm × 15 cm large sample stage) from EDAX Company to determine the distribution of characteristic elements of shooting residues, and established the distribution of relevant elements. The data model of characteristics changing with distance provides a scientific basis for distinguishing contact shooting, close shooting, short-range shooting and long-distance shooting.

Li Li and others from the Department of Forensic Medicine of Fudan University School of Medicine used Eagle III microbeam XRF of EDAX company in the United States to study the metallization of skin damaged by current, and detected the uneven distribution of metal elements that penetrated into the damaged skin, which was used as a diagnostic tool for current damage. Characteristic indicators provide a basis for the inference of electric shock materials. Su Huifang from the Department of Forensic Medicine, School of Medicine, Sun Yat-sen University, etc. comprehensively reviewed the application progress of MXRF technology in forensic identification.

The application of the MXRF test method in scientific and technological archaeology and identification of cultural relics is one of the most active application fields: at the beginning of this century, the Department of Science and Technology History and Archaeology of the University of Science and Technology of China and the City University of Hong Kong cooperated with the school’s EDAX company’s EAGLE-II μ-type energy Dispersive X-ray probe (EDXRF probe) has completed a number of ancient porcelain research. Since then, the Palace Museum, Shanghai Museum, and many archaeological and cultural institutions of Sun Yat-sen University, Northwest University and Wuhan University have adopted this type of instrument, especially with its type III instrument to carry out extensive non-destructive testing and research on archaeological cultural relics.

The School of Archaeology, Culture and Museology of Peking University used Shimadzu’s large-cavity microbeam XRF spectrometer EDX-800 HS to analyze and test the carcass and white powder layer components of a Ming Dynasty constellation painted sculpture in the Chunyang Palace in Taiyuan, Shanxi Province. Liang Yue from the Shaanxi Provincial Key Laboratory of Early Life and Environment, the State Key Laboratory of Continental Dynamics and the Department of Geology of Northwestern University used the M4 TORANDO high-performance microbeam X-ray fluorescence spectrometer developed by Bruker, Germany to analyze soft-body fossil specimens and enclosures.

Qualitative and quantitative analysis of the rock was carried out. The equipment has high spatial resolution and uses a polycapillary focusing mirror to focus the excitation light into a very small area (20 μm) to quickly image the element distribution in the same plane to obtain the chemical in the plane. Element distribution map and concentration distribution map, this study provides a method for researchers to study the semi-quantitative analysis of element composition and element distribution and concentration distribution map in fossils.

In terms of commodity inspection, Chen Chaofang from the Technical Center of Zhuhai Entry-Exit Inspection and Quarantine Bureau used HORIBA (Horiba) XGT-5200WR μ-EDXRF to analyze the distribution and content of potentially risky metal elements such as cobalt, chromium, manganese, and nickel in the glaze layer. It is convenient to quickly analyze the reasons for product defects to evaluate the quality and safety of products. The instrument adopts a Rh target X light pipe, a switchable X-ray pipe with a diameter of 100 μm and 1.2 mm, a silicon drift detector, and a 100 mm × 100 mm automatic two-dimensional sample moving platform with a step length of 2 μm.

2. MXRF analysis technology and application prospect

2.1 Analysis function positioning

As we all know, objects in nature are composed of elements (or nuclides), and natural substances (body), especially natural solid substances, are even more so. Since F.W. Clark published the data on the average content of elements in the earth’s crust in 1889, people have accumulated a lot of data on the content of elements in various objects and their regional distribution.

The composition and distribution of material elements are the most basic data in many fields of scientific research, resource development, industrial production, social development and human life. Although human beings have accumulated a huge amount of data ranging from the earth, cosmic celestial bodies, to many objects (mass) around human beings – including animals, plants and human beings’ own chemical composition, this is only a drop in the bucket for the vast and boundless natural world. With the development of human society, the requirements for the composition of various substances are also increasing rapidly, and the analysis technology to explore the elemental composition and distribution of substances is also developing rapidly.

The elemental composition data of objects (mass) are provided by various analysis techniques. The research on the content and distribution of elements in larger-scale (above centimeters) objects is completed by various traditional overall analysis techniques, while the micro-objects (or micro-areas) The content and distribution of elements in ) are provided by in situ (micro) analysis techniques. As far as the entire analysis technology system is concerned, the traditional overall analysis has developed earlier and is relatively mature, and the development of micro-area analysis technology, which is currently widely used, is relatively late, and its maturity is second only to the overall analysis, but the development space is huge.

The earliest developed various electron microbeam technologies (electron probes and various electron microscopes), the rapidly developed particle microbeam-based scanning proton (nuclear) probes (SPM, SNM) in the 1980s and 1990s, ion-based Microbeam-based ion probe mass spectrometry (SHRIMP), synchrotron radiation microbeam-based X-ray probe (SR-μXRF) and laser microbeam-based laser plasma mass spectrometry (LA-ICP-MS), etc. The formed micro-nano area analysis can now not only realize the determination of major, minor, trace elements or isotopes, but also an independent, multi-category micro-area analysis technology system that can perform micro-area element distribution analysis, which can be used for microscopic substances. Research provides a wealth of comprehensive, interdisciplinary scientific information. This type of micro-probe technology integrates a variety of high-tech technologies, and the size of the micro-beam has reached the micro-nano level.

At present, the application span (range) of its micro-area analysis reaches 5 to 6 orders of magnitude. This is the scope of application of any instrument or device, and it is difficult to achieve such a wide range of scales. As far as practical applications are concerned, the working area of micro-nano probes is mainly in the micro-nano area, and the micro-nano area is the nano-micro beam instrument, the microbeam XRF spectrometer (M-XRF). of use. Therefore, the former is called “micro-nano area analysis, μ/n-XRF”, while the latter is called “micro area analysis, μ/m-XRF”, which is more in line with the accurate positioning of its functions. The two together constitute the microbeam in-situ micro-analysis (MXRF) in XRF analysis. The two types of technology have different performances and functions. They are both closely related and relatively independent technical systems, covering the entire current in-situ micro-analysis. Scale range (nano-cm area). In this way, a complete technical system for inorganic component analysis from the whole to the in-situ micro-area is formed, which provides strong technical support for the analysis and research of material components at different scales and levels.

The basic requirements of micro-area analysis technology are: generally, it should have a sub-millimeter (50-500 μm) excitation beam spot and a sub-millimeter-centimeter-level scanning analysis range. Of course, it is better to have multi-element analysis capability with detection limit of μg·g-1. Its application areas are mainly in the elements and distribution of sub-millimeter-centimeter scale substances. The current research objects involve atmospheric particulate matter, scientific and technological archaeology, identification and protection of cultural relics, reconstruction of paleoenvironment and paleoclimate, criminal investigation science, geology, biology, environment and materials. Science and many other fields of technology. According to the current technical characteristics and application status of μ/m-XRF, it is one of the typical sub-milli-centi area analysis techniques, and is currently the most widely used and most important sub-milli-centi area analysis method. Therefore, it has become a new hotspot of research and application in the field of XRF technology.

Although the basic characteristics of micro-nano area analysis technology are similar to micro-nano area analysis technology and belong to non-destructive in-situ micro area analysis technology, there is still a big gap in spatial resolution and comprehensive detection and analysis performance. The level is still low, the application field is not wide enough, and the technical means are relatively simple. However, it still has its definite position in the positioning of the whole analysis function—the research method of micro- and nano-scale material composition characteristics (see Table 1).

Table 1 Analytical Technology and Functional Orientation

Classification Type Technical classification Result expression Function
Elemental analysis Overall analysis (determined after homogenization of a given sample) Primary, secondary and trace analysis (depending on element content) (Wet) chemical analysis: atomic spectroscopy (including: XRF, ICP-ES, AAS, AFS), Mass spectrometry (including: ICP-MS), electrochemical analysis, chromatographic analysis, nuclear analytical methods, photometric analysis, thermal analysis, … Average content of a given sample: Percentage (mass fraction)%, mg·g^-1, ng·g^-1, 10^-2, 10^-6, 10^-9 ≥10% (primary), 0.1% to 10% (secondary), <0.1% (scar)
Micron analysis (micron sub-millimeter spot, micron to milli-cm range), (CCD observation and constituency) Laser Microspectroscopy (LMS), Microbeam X-ray Fluorescence (Micro-XRF) 1. Sample morphology (optical or electronic image); 2. Percent content (mass fraction): %, μg·g^-1, ng·g^-1 or 10^-2, 10^-6, 10^-9; 3. Element 2 or 3 dimensional distribution map Topography observation, fixed-point analysis, distribution analysis (point by point or scan)
Micro-area (micro) analysis (In situ determination or distribution analysis of tiny samples or tiny areas) Micro-nano analysis (micron sub-micron spot, sub-micron to sub-millimeter range), (CCD observation and selection) Various types of micro-submicron microbeams: Micro-nano beam spot: 1. electronic probe, Various electron microscopes (electron microbeam) (EM-PA, SEM, STM, SAM); 2. Proton (nuclear) probes (particle micro beam) (PMPA, SPM, SNM, μ-PIXE); 3. Ion probe mass spectrometry (ion beam) (IMPA, SHIMP); 4. Synchrotron radiation X-ray probe (X-ray beam) (XM- PA, SR-μ-XRF); 5. Laser Plasma Mass Spectrometry (Laser Beam) (LMPMS, LA-ICPMS) 1. Sample morphology (optical or electronic image); 2. Percent content (mass fraction): %, μg·g^-1, ng·g^-1 or 10^-2, 10^-6, 10^-9; 3. Element 2 or 3 dimensional distribution map Topography observation, fixed-point analysis, distribution analysis (point-by-point or scan)

Such technical distinction and application scope positioning are beneficial to the technical development of micro-area analysis, and also clarify the direction for the development and application of integral/micro-area combined instruments.

2.2 Technology Development

The key part of the μ/m-XRF analysis device is the microbeam X-ray source, the core of which is the X-ray optical element with the function of focusing. Given the unique propagation properties of X-rays, the regulation of X-rays has always been a major challenge in their applications. In the 1980s, with the development of catheter X-ray optics, especially the development of polycapillary X-ray lens and other technologies, the X-ray condenser light source has undergone revolutionary changes. Efficient microbeam X light sources provide a variety of options, effectively promoting the rapid development of MXRF since the 1990s.

Nevertheless, compared with the development and application level of μ/m-XRF technology and the relatively mature overall analysis technology and micro (nano) area analysis technology, there is still a big gap. Therefore, its technology and application have great development. space. As far as the analysis function positioning and application of μ/m-XRF is concerned, the development of its technology and application is more worthy of attention in the following aspects:

(1) Focusing element and its performance improvement At present, there are many kinds of optical elements for X-ray focusing, but for μ/m-XRF, capillary optical elements are mainly used: especially the polymeric capillary lens, especially the integral X-ray optics that is gathered by tens of thousands of capillaries Lens (Drawn Kumakhov Lens). The micro-X-ray source with high spatial resolution and intensity gain is of course an important research direction of μ/m-XRF. Technology ranks. Although this is a very interesting research direction, for the most realistic application of μ/m-XRF, the lateral resolution of tens of microns can basically meet the needs of μ/m-XRF analysis functions. If the source can reduce the incident focal length, improve the transmission efficiency and improve the uniformity of the output rays and other properties, it will be an important requirement for high-quality microbeam X-ray sources.

(2) Comprehensive performance of the whole machine In terms of application, more attention should be paid to the overall performance of the μ/m-XRF device. In recent years, in addition to the design and improvement of a variety of microbeam light sources, there has also been great progress in detection and reception systems. The research team of Beijing Normal University used a catheter X-ray lens and a position-sensitive proportional counter to form a micro-X fluorescence analyzer with high spatial resolution, high energy resolution, and high sensitivity, and used two polycapillary X-ray lenses to build a confocal microbeam X-ray spectrometer. The ray fluorescence spectrometer greatly improves the performance of the whole machine and expands the application range from different aspects. Wang Junjie’s group at Zhejiang University of Technology designed a microbeam XRF spectrometer consisting of an X-ray focusing capillary lens (incident) and an X-ray combined refracting lens (exit). The combined refractive lens is designed to be detachable, and the distance between the detector and the lens is adjustable. The system can effectively improve the spatial resolution, sensitivity, and expand the scope of elemental analysis.

From the perspective of the mechanical system design of the instrument, Ge Liangquan’s team from Chengdu University of Technology studied the design requirements and implementation methods to achieve high precision, intelligence and miniaturization of the mechanical system, so as to improve the overall efficiency of the instrument. In view of the μ/m-XRF device not only to complete the fixed-point quantitative analysis of the selected region of interest, but also to perform area scanning to realize the distribution analysis of elements in many cases. Standard materials, matrix calibration methods based on the basic parameter method, and graphical (gray (chromatic) or contour map) software of various element maps (line, surface and depth distribution) are also important development studies to improve instrument performance. content. The development of μ/m-XRF analysis technology is not long in general, the device design has not been standardized and serialized, and its application technology is far from standardized, and it will take a long journey to further improve the performance of the whole machine.

From the literature, the Eagle II and Eagle III microbeam X-ray fluorescence spectrometers (μ-probe) of EDAX Corporation of the United States are widely used in China, especially in the fields of scientific and technological archaeology and criminal investigation.

(3) μ/m-XRF in a multifunctional combined instrument In large-scale spectrum or spectrum/energy spectrum combined instruments, most of the micro-beam X-ray excitation sources are obtained by collimated micro-beam. Although the high-power X-ray tubes used in such instruments have sufficient light intensity, optimizing the microbeam characteristics is still an important research direction in the future. In addition, the incidence of excitation radiation, the geometric structure design of the sample and fluorescence emission detection, the design of the sample stage and the improvement of the scanning method are all important research directions. Compared with the μ/m-XRF stand-alone instrument, the μ/m-XRF device in the combined instrument has a larger beam spot, but its scanning function should be emphasized and the element map with better visual effect should be given.

3. Conclusion

Different from applications in bulk XRF analysis: μ/m-XRF analysis technology (including μ/m-XRF in multifunctional instruments) and microbeam area analysis technology, elemental distribution analysis-element mapping is its most important application function . This function is not only a simple analysis and testing problem, but more importantly, the research on the characteristics of the tested material (sample)! Therefore, the close cooperation between analytical technicians and relevant professional scientists is required to give full play to the advantages of this in-situ analysis technology. Efficacy, through the interpretation of test results, shows its scientific significance and further expands the application scope of MXRF analysis technology. In addition to the testing technology itself, the participation and cooperation of relevant professional researchers is the most important factor in the development of such technology.

Overview of polycapillary X-ray optics >