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Discover C f AM

Discover C f AM. X-ray microanalysis in the electron microscope Needs to be longer!. X-ray microanalysis in the electron microscope. X-ray microanalysis in EMLab. Oxford Instruments – INCA software. X-ray microanalysis. How are X-rays generated?.

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Discover C f AM

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  1. Discover CfAM X-ray microanalysis in the electron microscope Needs to be longer! X-ray microanalysis in the electron microscope

  2. X-ray microanalysis in EMLab Oxford Instruments – INCA software

  3. 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)

  4. Signals in the electron microscope

  5. Ejection of inner electron and transition between shells characteristic X-rays Generation of X-rays Deceleration of electrons background X-rays

  6. Generation of X-rays

  7. Energy dispersive X-ray spectrum Atomic levels involved in copper Kα and Kβ emission

  8. Energy dispersive X-ray spectrum

  9. Energy dispersive X-ray spectrometer

  10. 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

  11. X-ray voltage pulse pulse processor Pulse processing

  12. Process time 6 Process time 1 Processing time (dead time)

  13. Practical EDX on the Quanta ► Aperture 3 ► Turn off chamber camera ► Set Process Time

  14. EDX results

  15. INCA options

  16. Point & ID Single point Selected region Line of points Grid of points

  17. Mapping

  18. Tracey Finn/Amy Smith (Ure Museum) Fragments of Egyptian pot Mapping

  19. Mapping Experimental Archaeology: Flint knapping of antler tools

  20. Wavelength dispersive X-ray spectrometer

  21. Crystal Analyzing range, eV Lithium Fluoride Pentaerythritol 15,330 - 4,712 4,994 - 1,535 Wavelength dispersive X-ray spectrometry Bragg diffraction

  22. X-ray Ionises counter gas Electrical pulse Wavelength dispersive X-ray spectrometry Gas proportional counter – contains 90% argon, 10% methane

  23. Wavelength dispersive X-ray spectrometry • Advantages High resolution High sensitivity • Disadvantages Slow - spectrum acquired sequentially Cannot be used at low magnifications

  24. Standards need to be run for all elements to be analysed Wavelength dispersive X-ray spectrometry Not necessary for EDX, because EDX intensities can be simulated

  25. Questions? • Demo

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