MICROSCOPIC X-RAY FLUORESCENCE ANALYSIS Edited by

Koen H.A. Janssens, Freddy C.V. Adams Department of Chemistry, University of Antwerp, Belgium

Anders Rindby Department of Physics, Chalmers University of Technology, Göteborg, Sweden

JOHN WILEY & SONS, LTD Chichester • New York • Weinheim • Brisbane • Toronto • Singapore

CONTENTS

CONTRIBUTORS xi

PREFACE xiii

1 OVERVIEW 1 K. Janssens, F. Adams and A. Rindby

1.1 Introduction 1 1.2 Laboratory /u-XRF 2 1.3 Synchrotron/i-XRF 6 References 10

2 INTERACTION OF X-RAYS WITH MATTER 17 J.E Fernändez

2.1 Introduction 17 2.2 Relevant aspects of photon interactions with matter 18 2.3 Single-process kerneis 20

2.3.1 Representation of polarized radiation with Stokes parameters 21

2.3.2 Photoelectric effect 24 2.3.3 Rayleigh scattering 28 2.3.4 Compton scattering 30

2.4 Mathematical description of photon diffusion 38 2.4.1 Scalar transport equation 39 2.4.2 Vector transport equation 41 2.4.3 Differences and similarities between the scalar

and vector modeis 44 2.5 Interpretation of X-ray fluorescence spectra 48

2.5.1 Advantages and limitations of the transport model for describing X-ray diffusion 49

2.5.2 Example 56 References 59

3 MICROFOCUSING X-RAY OPTICS 63 A. Rindby, F. Adams and P. Engström

3.1 Introduction 63 3.2 Basic imaging and non-imaging optics 64

VI CONTENTS

3.2.1 Collimators and focusing Systems 64 3.2.2 Early focusing Systems 65 3.2.3 Kirkpatrick-Baez optics 66 3.2.4 Modern focusing Systems 66 3.2.5 Imaging versus non-imaging Systems 66

3.3 X-ray optics, aberration and astigmatism 68 3.3.1 Optical theory of X-rays 68 3.3.2 Fresnel formula 70 3.3.3 Total reflection 72 3.3.4 Geometrical aberrations 73 3.3.5 Flux, brightness and brilliance 74

3.4 Mirror optics 74 3.4.1 Multilayer optics 74 3.4.2 Grazing incidence mirrors 75 3.4.3 Compound Systems 76

3.5 Capillary optics 77 3.5.1 Historical background 77 3.5.2 Monocapillary shapes and dimensions 78 3.5.3 Propagation of X-rays inside a capillary 79 3.5.4 Ray-tracing - experimental results 83 3.5.5 Capillary optics in practice 85 3.5.6 Polycapillary (Kumakhov) lenses 87

3.6 Refractive optics 87 3.7 Fresnel and Bragg-Fresnel optics 89

3.7.1 Fresnel zoneplates 90 3.7.2 Bragg-Fresnel optics 92

3.8 Conclusions 93 References 93

INSTRUMENTATION FOR fi-XRF WITH LABORATORY SOURCES 95 A. Rindby

4.1 Historical perspective 95 4.2 Basic components 96

4.2.1 X-ray tube intensity and brilliance 96 4.2.2 Focusing devices 99 4.2.3 Sample positioning and monitoring 101 4.2.4 Detection System and signal processing 103

4.3 Scanning procedure 104 4.4 Visualization and image processing 106 4.5 Sensitivity 108 4.6 Fiat (rectangular) beam technology 110 4.7 Converting existing XRF equipment to /i-XRF

application 111

CONTENTS Vll

4.8 Commercial Instrumentation 112 4.9 High-flux Instrumentation 113 References 114

5 INSTRUMENTATION FOR /u-XRF AT SYNCHROTRON SOURCES 117 A. Iida

5.1 Introduction 117 5.2 Synchrotron radiation sources 117

5.2.1 General properties of Synchrotron radiation 117 5.2.2 Synchrotron radiation from bending magnets 121 5.2.3 Insertion devices 124 5.2.4 Storage ring and phase-space electron ellipse 127

5.3 Micro-XRF Instrumentation at a Synchrotron radiation facility 129 5.3.1 Fundamental aspects of SR-excited X-ray

fluorescence analysis V 129 5.3.2 Beamline layout for an X-ray microbeam facility 132

5.4 SR techniques for material characterization 139 5.4.1 X-ray absorption fme structure analysis 139 5.4.2 X-ray microdiffraction 145 5.4.3 Microtomography 147

References 150

6 EVALUATION AND CALIBRATION OF/u-XRF DATA 155 K. Janssens, L. Vincze and B. Vekemans

6.1 Introduction 155 6.2 Spectrum evaluation 156 6.3 Image processing and Interpretation 163

6.3.1 Color encoding 163 6.3.2 Segmentation of multivariate data sets 164

6.4 Quantitative analysis 169 6.4.1 General considerations 169 6.4.2 Fundamental parameter method 170 6.4.3 Information depth 182 6.4.4 Self-absorption correction in heterogeneous samples 183 6.4.5 Conditions for local homogeneity - factors

determining lateral resolution 190 6.4.6 Prediction of the spectral response of /u-XRF

spectrometers 192 6.4.7 Analytical model for /z-XRF analysis of individual

particles 202 6.4.8 Detection of systematic variations in /u-XRF

data due to topological effects 202

Vlll CONTENTS

6.5 XRF tomography 204 References 207

COMPARISON WITH OTHER MICROANALYTICAL TECHNIQUES 211 K. Janssens

7.1 Introduction 211 7.2 Microscopic X-ray emission techniques 215

7.2.1 Beam penetration and flux density 215 7.2.2 Detection limits 218 7.2.3 Analysis of microscopic particles 222 7.2.4 Combination with other modes of analysis 224

7.3 Imaging, lateral resolution and depth resolution 226 7.4 Sensitivity 229 7.5 Accuracy and precision 231

7.5.1 Meteorites 233 7.5.2 Synthetic glasses and melt inclusions 233 7.5.3 REE analysis in Standard glasses 233 7.5.4 Analysis of REE and related elements in fossils 238

7.6 Beam-induced damage 239 7.7 Laboratory ^-XRF 240

7.7.1 Analysis of glass fragments 242 7.8 Conclusions 242 References . 243

APPLICATIONS IN THE GEOLOGICAL SCIENCES 247 Keith W. Jones

8.1 Introduction 247 8.2 Synchrotron radiation experimental beam lines 248 8.3 Synchrotron radiation induced X-ray fluorescence

(SRXRF) 251 8.3.1 Extraterrestrial materials 251 8.3.2 Fluid inclusions 253 8.3.3 Ore formation 254 8.3.4 Determination of metals in Sediments and in pore

water 257 8.3.5 Detection of rare earth elements 262 8.3.6 Trace elements in minerals 265

8.4 X-ray diffraction 267 8.5 High-pressure experiments 269 8.6 Computed tomography experiments 271 8.7 XANES and EXAFS 279 8.8 Summary 284

IX

Acknowledgments 285 References 285

APPLICATIONS IN ART AND ARCHAEOLOGY 291 K. Janssens and F. Adams

9.1 Introduction 291 9.2 Trace element fmgerprinting 293

9.2.1 Trace analysis of historic glass 293 9.2.2 Analysis of inks 298

9.3 Microscopic analysis 299 9.3.1 Glass corrosion 299 9.3.2 Inclusions in iron artefacts 303

9.4 Local analysis of macroscopic objects 304 9.4.1 Enamel decorations 304 9.4.2 Coins and statues 306 9.4.3 Ink on handwritten documents 308

9.5 Towards in-situ /^-XRF investigations 308 9.5.1 Laboratory-built equipment 309 9.5.2 Commercial equipment 309 9.5.3 Compact focusing optics 310

9.6 Conclusions 311 References 312

ENVIRONMENTAL AND BIOLOGICAL APPLICATIONS OF/z-XRF 315 Jänos Osän, Szabina Török, Anders Rindby 10.1 Industrial Applications of/x-XRF 315 10.2 Single-particle analysis 316

10.2.1 Atmospheric particles 318 10.2.2 Single aerosol particle analysis 318 10.2.3 Analysis of fly-ash 320 10.2.4 Trace element analysis of individual particles 321 10.2.5 Elemental imaging of single particles 321 10.2.6 Elemental mapping of particles deposited on

plant surfaces 325 10.2.7 Chemical State of specific elements in single

particles 327 10.2.8 Combined microfluorescence and microdiffraction

analysis 329 10.3 Analysis of tree rings and wood tissues 330

10.3.1 Trace element composition of tree rings 333 10.3.2 Trace element analysis of single fibres in wood

tissues 334

CONTENTS

10.3.3 Density variations between and within individual rings 336

10.4 Other environmentally oriented biological applications 341 References 342

INDUSTRIAL APPLICATIONS OF />XRF 347 Donald A. Carpenter 11.1 Introduction 347 11.2 Plating and film thickness 348 11.3 Waste characterization 351

11.3.1 Electronic components 351 11.3.2 Development of new disposal methods 354

11.4 Forensics 358 11.4.1 Hairanalysis 358 11.4.2 Particle analysis 361

11.5 Homogeneity of steel alloying elements 361 11.6 Materials analysis in the industrial laboratory 362

11.6.1 Analysis of metal pins 362 11.6.2 Analysis of spray nozzle 364 11.6.3 Analysis of amalgamated metal powders 364 11.6.4 Analysis of automobile catalyst 366 11.6.5 Characterization of moved oxide fuel Surrogate

feed material 366 11.7 Materials science applications using Synchrotron

radiation 366 11.8 Conclusions 367 Acknowledgments 368 References 368

THE FUTURE OF /x-XRF 371 F. Adams and K. Janssens 12.1 Introduction 371

12.1.1 Laboratory/z-XRF 371 12.1.2 Synchrotron radiation based/x-XRF 373 12.1.3 Detection and spectrometry of X-rays 376

12.2 Analytical characteristics 379 12.3 Quantitative analysis 380 12.4 Prospects 382

12.4.1 Laboratory/i-XRF 382 12.4.2 Synchrotron radiation /z-XRF 382

12.5 Summary 388 References 388

393