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Discover C f AM
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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
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Generation of X-rays
Deceleration of electrons background X-rays
Ejection of inner electron and transition between shells characteristic X-rays
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Generation of X-rays
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Energy dispersive X-ray spectrum
Atomic levels involved in copper Kα and Kβ emission
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Energy dispersive X-ray spectrum
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Energy dispersive X-ray spectrometer
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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
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Pulse processing
voltage pulse pulse processorX-ray
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Processing time (dead time)
Process time 6
Process time 1
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Practical EDX on the Quanta
► Aperture 3 ► Turn off chamber camera ► Set Process Time
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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
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INCA options
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Point & ID
Single pointSelected regionLine of pointsGrid of points
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Mapping
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Mapping
Tracey Finn/Amy Smith (Ure Museum)
Fragments of Egyptian pot
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Mapping
Experimental Archaeology:
Flint knapping of antler tools
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Wavelength dispersive X-ray spectrometer
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Wavelength dispersive X-ray spectrometry
Bragg diffraction
Analyzing range, eVCrystal
Lithium Fluoride 15,330 - 4,712
Pentaerythritol 4,994 - 1,535
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Wavelength dispersive X-ray spectrometry
Gas proportional counter – contains 90% argon, 10% methane
Ionises counter gas
X-ray
Electrical pulse
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Wavelength dispersive X-ray spectrometry
Advantages
High resolution
High sensitivity
Disadvantages
Slow - spectrum acquired sequentially
Cannot be used at low magnifications
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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