Carlos A. Pérez

(carlos.perez@lnls.br)

Grupo de Absorção e Fluorescência de Raios-X

Laboratório Nacional de Luz Síncrotron (LNLS/CNPEM)

Techno-scientific meeting on applications of

synchrotron radiation to geosciences

LNLS July 2, 2014

Carlos A. Pérez

Researcher - XRF beamline coordinator

e-mail: carlos.perez@lnls.br

Brazilian Synchrotron Light Laboratory (LNLS)

Brazilian Center for Research in Energy and Materials (CNPEM) Campinas-SP, Brazil

INTRODUCTION TO SR-XRF MICROSCOPY AND QUANTITATIVE ANALYSIS

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

TRANSMITTED X-RAYS

MATTER

SCATTERING

Compton Rayleigh

ABSORPTION

PAIR PRODUCTION(Eo > 1 MeV)

INCOMING X-RAYS

DECAY PROCESSES

• X-Ray Fluorescence • Auger e-

• Secondary e-

EooE

E´o< EoEf

Io(Eo) I(Eo)= Io(Eo)e-m(Eo)rx

(Radiatives) (Non radiatives)

• XEOL

Interaction of X-rays with matter

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

X-Ray Fluorescence (XRF) consist of an emission of characteristic orsecondary x-rays of the atoms from the material excited by x-rays of highenergy.

Atom

Radiative decay process

X-Ray Fluorescence (XRF)

Photoelectric effect

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

X-Ray Fluorescence (XRF) is a very efficient radiation decay process fortransition and heavy elements which are normally found in low concentrationin nature.

X-rays vs. Auger

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

NIST 1577b

(Bovine Liver)

Incident beam sample

Detector (EDX)

PreAmp

Amp

MCA

X-ray fluorescence and

scattering from the

sample

Micro

a

X-ray Fluorescence: spectrum measurement

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

High Flux and Brilliance.

Broad spectral range.

High degree of linear polarization.

Synchrotron Radiation (SR) Properties:

High sensitivity for TRACE ELEMENTS DETECTION IN MICROSCOPICS AREAS or in

small volume from the bulk

White or monochromatic excitation. Simultaneous excitation of several element

(MULTIELEMENTAR ANALYSIS)

background reduction DETECTION LIMITS IMPROVEMENT

Almost NON-DESTRUCTIVE analytical method

Analytical Improvements of XRF using SR:

Microscopic XRF analysis with synchrotron radiation

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

OPTICS FOR X-RAY MICROBEAM GENERATION

Pinhole /Collimation

Pair of mirrors

Mono/Policapillaries

Refraction lenses

Zones Plates

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

Scanning X-ray microscope arrangements

After J. Susini

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

X-ray microbeam

X-rayMicrobeam

EDXRS

Irradiated Area

Raster scanning of the sample through the x-ray microbeam

m-XRF analysis (2D)

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

m-XRF tomography (3D)

Elemental maps of a single slice obtained after

tomographic reconstruction of X scans

x

ED-detector

Elemental sinograms

X-rays

K Mn

Fe Zn

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

Photo-absorption Excited State Relaxation

X-ray

Fluorescent

X-ray

Auger electronO

ccu

pie

d

Ele

ctr

on

ic

Sta

tes

Un

oc

cu

pie

d

Ele

ctr

on

ic

Sta

tes

(electron ejection or promotion)

X-ray Absorption & Fluorescence

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

X-ray Absorption spectroscopy

1) Transmission

Synchrotron radiation

source

monochromatorIo I

sample

Ion chambers

I

It 0logm

2) Fluorescence

Io

sample

Scintilator / Si(Li)/

Ge-15 elements/

Silicon drift

0I

Fyt m

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

ioo

io

dEE

i

K

io

K

iiif mEIdEE

epEEgI

io

)(),(

1)()(

),(

,

r

r

First-order approximation (no enhancement effect)

Io(Eo)

If,i

)sin(

)(

)sin(

)(),(

21

m

m io

io

EEEE

r

)()()()( oincocohoo EEEE m

i

oiio ECE )()( mm 1i

iC;

Geometrical factors

Fundamental parameters interelement effect

(sample absorption factor)

Incoming intensity

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

• Characteristics Lines.

• Background.

• Peak shape correction, escape

peaks and sum peaks.

Characteristic lines

Background

Fit a Mathematical Model of ED-XRF Spectrum to the Experimental Data

XRF spectrum evaluation

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

Escape and Sum Peaks

Escape peaks arise when strong

elements is recorded by the

detector

Sum peaks are expected when a

few large peaks at lower energies

dominate the spectrum.

XRF spectrum evaluation

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

Mathematical methods:

Compensation methods:

• Influence Coefficients Algorithms

• Fundamental Parameter (FP)

• Monte Carlo Simulation

• Multivariate Calibration methods

• Scattered radiation

• Internal standard

• standard addition

• Dilution methods

Eliminate or measure the interelement effects

Calculate the interelement effects

XRF spectrum evaluation

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

Software package for XRF spectra evaluation

•QXAS (Quantitative X-ray Analysis System), quantitative evaluation of spectra measured

by ED-XRF.

•AXIL (Analysis of X-ray spectra by Iterative Least-squares fitting) package for the

determination of net peak areas of the characteristic lines of interest.

• WINAXIL (Canberra).

• PyMCA (Phyton Multichannel Analyzer). A multiplatform code for the analysis of ED-XRF

spectra developed by Beamline Instrumentation Software Support (BLISS) group at the

ESRF.

XRF spectrum evaluation

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

HANDS-ON

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

Ca

Fe Zn

Sum peaksEscape peaks

Qualitative Analysis

Identify characteristic peaks and artifacts in the EDXRF spectrum

After data collection …

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

Fit experimental data to a mathematical model using a software package for EDXRF

PyMca has been developed by the Beamline Instrumentation Software Support (BLISS) group of the European Synchrotron Radiation Facility (ESRF).

EDXRF Spectrum Evaluation

V. A. Solé, E. Papillon, M. Cotte, Ph. Walter, J. Susini, A multiplatform code for the analysis of energy-dispersive X-ray fluorescence spectra, Spectrochim. Acta B 62 (2007) 63–68.

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

EDXRF Spectrum Evaluation

Starch doped with Zn

Reference material

C6H10O5 -> (0.999995)+Zn -> (5e-06)

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

EDXRF Spectrum Evaluation

Spectrum energy calibration

Save calibration file!

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

Spectrum fitting

EDXRF Spectrum Evaluation

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

EDXRF Spectrum Evaluation

Spectral distribution of the incoming beam

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

EDXRF Spectrum Evaluation

Io

If,i

r

Beam Filter

Filter

i

oiio ECE )()( mm

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

Calibration using the information from the reference material

XRF Quantitative Procedure

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

XRF Quantitative Procedure

Unknown sample (reference material 25 ppm)

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

XRF Quantitative Procedure

Batch mode operation

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

XRF Quantitative Procedure

Credits: Marcela Nunes (CENA/USP)

XRF mapping of maize seed (cross-section)

Zn

S P

Carlos A. Pérez (LNLS/CNPEM) 5th School on X-ray Spectroscopy Methods August, 22nd- 23th 2016

SUGGESTED BOOK FOR READING

THANK YOU FOR YOUR ATTENTION !