X-rays

1. Long Wave IR Visible UV X-rays Gamma rays 1012 106 103 10 1 10-1 10-3 wavelength (nm) X-rays Frau Röntgen's hand

2. Long Wave IR Visible UV X-rays Gamma rays 1012 106 103 10 1 10-1 10-3 wavelength (nm) X-rays

3. X-ray tube

4. X-ray tube

5. X-rays

6. X-rays White radiation Produced upon "collisions" with electrons in target Any amount of energy can be lost up to a max. amount Continuous variation of wavelength Characteristic radiation Specific energies absorbed Specific x-ray wavelengths emitted Wavelengths characteristic of target atom type

7. X-rays Mechanism Decelerating charges give off radiation

8. X-rays Mechanism Decelerating charges give off radiation

9. X-rays Mechanism Decelerating charges give off radiation

10. X-rays Mechanism Decelerating charges give off radiation

11. X-rays Mechanism Decelerating charges give off radiation

12. X-rays Typical tube spectrum

13. Iconts = AiZV~2 Ichar = Ai(V-Vcrit)~1.5 E >> hc/Kedge E > hc/Kedge E ≈ hc/Kedge X-rays - vary tube voltage Intensity Wavelength

14. X-rays More electron transitions

15. X-rays Cu spectrum

16. X-rays Al spectrum

17. X-rays Au L spectrum

18. X-rays Moseley's law - energy vs. atomic number

19. X-ray sources Sealed tubes - Coolidge type common - Cu, Mo, Fe, Cr, W, Ag Ka = (2 Ka1 + Ka2)/3

20. X-ray sources Sealed tubes - Coolidge type common - Cu, Mo, Fe, Cr, W, Ag intensity limited by cooling requirements (2-2.5kW) (~99% of energy input converted to heat)

21. Intensity changes with take-off angle  But resolution decreases with take-off angle X-ray sources

22. X-ray sources

23. Other X-ray sources Rotating anode high power - 40 kW demountable various anode types

24. Other X-ray sources Synchrotron need electron or positron beam orbiting in a ring beam is bent by magnetic field x-ray emission at bend Advantages 10-4 - 10-5 radians divergence (3-5 mm @ 4 m) high brilliance wavelength tunable

25. Other X-ray sources Synchrotron Advantages 10-4 - 10-5 rad divergence (3-5 mm @ 4 m) high brilliance wavelength tunable

26. Other X-ray sources Synchrotron need electron or positron beam orbiting in a ring beam is bent by magnetic field x-ray emission at bend Advantages 10-4 - 10-5 rad divergence (3-5 mm @ 4 m) high brilliance wavelength tunable high signal/noise ratio

27. X-ray sources Synchrotron Advantages 10-4 - 10-5 rad divergence (3-5 mm @ 4 m) high brilliance wavelength tunable

28. X-ray sources Synchrotron Advantages 10-4 - 10-5 rad divergence (3-5 mm @ 4 m) high brilliance wavelength tunable

29. Beam conditioning Collimation

30. X-rays detector filter specimen Beam conditioning Monochromatization -filters – materials have atomic nos. 1 or 2 less than anode 50-60% beam attenuation placing after specimen/before detector filters most of specimen fluorescence allows passage of high intensity & long wavelength white radiation

31. Beam conditioning Monochromatization -filters – materials have atomic nos. 1 or 2 less than anode 50-60% beam attenuation placing after specimen/before detector filters most of specimen fluorescence allows passage of high intensity & long wavelength white radiation

32. Beam conditioning Monochromatization Crystal monochromators – LiF, SiO2, pyrolytic graphite critical – reflectivity ex: for MoK, LiF 9.4% graphite 54 %

33. Beam conditioning Monochromatization Crystal monochromators – LiF, SiO2, pyrolytic graphite critical – reflectivity ex: for MoK, LiF 9.4% graphite 54 % resolution – determines peak/bkgrd ratio & spectral purity best - Si – 10" graphite – 0.52°

34. Beam conditioning Monochromatization Monochromator shape usually flat – problems with divergent beams concentrating type – increases I by factor of 1.5-2