carlos a. pérez ([email protected]) introduction to sr...

Carlos A. Pérez

([email protected])

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: [email protected]

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

mailto:[email protected]

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


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


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


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


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


OPTICS FOR X-RAY MICROBEAM GENERATION

Pinhole /Collimation

Pair of mirrors

Mono/Policapillaries

Refraction lenses

Zones Plates


Scanning X-ray microscope arrangements

After J. Susini


X-ray microbeam

X-rayMicrobeam

EDXRS

Irradiated Area

Raster scanning of the sample through the x-ray microbeam

m-XRF analysis (2D)


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


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


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


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


• 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


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.



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



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.



HANDS-ON


Ca

Fe Zn

Sum peaksEscape peaks

Qualitative Analysis

Identify characteristic peaks and artifacts in the EDXRF spectrum

After data collection …


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.



Starch doped with Zn

Reference material

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



Spectrum energy calibration

Save calibration file!


Spectrum fitting




Spectral distribution of the incoming beam



Io

If,i

r

Beam Filter

Filter

i

oiio ECE )()( mm


Calibration using the information from the reference material

XRF Quantitative Procedure



Unknown sample (reference material 25 ppm)



Batch mode operation



Credits: Marcela Nunes (CENA/USP)

XRF mapping of maize seed (cross-section)

Zn

S P


SUGGESTED BOOK FOR READING

THANK YOU FOR YOUR ATTENTION !

carlos a. pérez ([email protected]) introduction to sr...

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