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www.reading.ac.uk/ cfam © University of Reading 2007 Discover CfAM X-ray microanalysis in the electron microscope X-ray microanalysis in the electron microscope Needs to be longer!
Discover CfAMX-ray microanalysis in the electron
microscope
X-ray microanalysis in the electron microscope Needs to be longer!
EM Workshop November 27th 2013
X-ray microanalysis in EMLab
Oxford Instruments – INCA software
EM Workshop November 27th 2013
X-ray microanalysis
How are X-rays generated?
How are X-rays detected? - Energy dispersive X-ray spectrometry (EDX)
Practical EDX – Point & ID; Mapping
Wavelength dispersive X-ray spectrometry (WDX)
EM Workshop November 27th 2013
Signals in the electron microscope
EM Workshop November 27th 2013
Generation of X-rays
Deceleration of electrons background X-rays
Ejection of inner electron and transition between shells characteristic X-rays
EM Workshop November 27th 2013
Generation of X-rays
EM Workshop November 27th 2013
Energy dispersive X-ray spectrum
Atomic levels involved in copper Kα and Kβ emission
EM Workshop November 27th 2013
Energy dispersive X-ray spectrum
EM Workshop November 27th 2013
Energy dispersive X-ray spectrometer
EM Workshop November 27th 2013
Lithium-drifted silicon detector
X-ray electron-hole pair
voltage pulse proportional to energy of X-ray Pulses are amplified, processed and sent to multichannel analyser
EM Workshop November 27th 2013
Pulse processing
voltage pulse pulse processorX-ray
EM Workshop November 27th 2013
Processing time (dead time)
Process time 6
Process time 1
EM Workshop November 27th 2013
Practical EDX on the Quanta
► Aperture 3 ► Turn off chamber camera ► Set Process Time
EM Workshop November 27th 2013
EDX results
FeCaCa
Fe Fe
C
K
KCa
Na
K
Al
O Si
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8keVFull Scale 2499 cts Cursor: 4.760 (39 cts)
Spectrum 1
EM Workshop November 27th 2013
INCA options
EM Workshop November 27th 2013
Point & ID
Single pointSelected regionLine of pointsGrid of points
EM Workshop November 27th 2013
Mapping
EM Workshop November 27th 2013
Mapping
Tracey Finn/Amy Smith (Ure Museum)
Fragments of Egyptian pot
EM Workshop November 27th 2013
Mapping
Experimental Archaeology:
Flint knapping of antler tools
EM Workshop November 27th 2013
Wavelength dispersive X-ray spectrometer
EM Workshop November 27th 2013
Wavelength dispersive X-ray spectrometry
Bragg diffraction
Analyzing range, eVCrystal
Lithium Fluoride 15,330 - 4,712
Pentaerythritol 4,994 - 1,535
EM Workshop November 27th 2013
Wavelength dispersive X-ray spectrometry
Gas proportional counter – contains 90% argon, 10% methane
Ionises counter gas
X-ray
Electrical pulse
EM Workshop November 27th 2013
Wavelength dispersive X-ray spectrometry
Advantages
High resolution
High sensitivity
Disadvantages
Slow - spectrum acquired sequentially
Cannot be used at low magnifications
EM Workshop November 27th 2013
Wavelength dispersive X-ray spectrometry
Standards need to be run for all elements to be analysed
Not necessary for EDX, because EDX intensities can be simulated
EM Workshop November 27th 2013
Questions?
Demo
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