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X-rays 10 12 10 6 10 3 10 1 10 -1 10 -3 Long Wave IR Visible UV X-rays Gamma rays wavelength (nm) Frau Röntgen's hand.

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Presentation on theme: "X-rays 10 12 10 6 10 3 10 1 10 -1 10 -3 Long Wave IR Visible UV X-rays Gamma rays wavelength (nm) Frau Röntgen's hand."— Presentation transcript:

1 X-rays Long Wave IR Visible UV X-rays Gamma rays wavelength (nm) Frau Röntgen's hand

2 Long Wave IR Visible UV X-rays Gamma rays wavelength (nm) X-rays

3 X-ray tube

4

5 X-rays

6 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 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 Mechanism Decelerating charges give off radiation

8 X-rays Mechanism Decelerating charges give off radiation Mechanism Decelerating charges give off radiation

9 X-rays Mechanism Decelerating charges give off radiation Mechanism Decelerating charges give off radiation

10 X-rays Mechanism Decelerating charges give off radiation Mechanism Decelerating charges give off radiation

11 X-rays Mechanism Decelerating charges give off radiation Mechanism Decelerating charges give off radiation

12 X-rays Typical tube spectrum

13 X-rays - vary tube voltage Intensity Wavelength E ≈ hc/ Kedge E >> hc/ Kedge E > hc/ Kedge I conts = AiZV ~2 I char = Ai(V-V crit ) ~1.5

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

22 X-ray sources

23 Other X-ray sources Rotating anode high power - 40 kW demountable various anode types 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 Synchrotron need electron or positron beam orbiting in a ring beam is bent by magnetic field x-ray emission at bend Advantages radians divergence (3-5 4 m) Advantages radians divergence (3-5 4 m) high brilliance wavelength tunable high brilliance wavelength tunable

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

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

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

29 Beam conditioning Collimation

30 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 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 X-rays detector filter specimen

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 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, SiO 2, pyrolytic graphite critical – reflectivity ex: for MoK , LiF 9.4% graphite 54 % Monochromatization Crystal monochromators – LiF, SiO 2, pyrolytic graphite critical – reflectivity ex: for MoK , LiF 9.4% graphite 54 %

33 Beam conditioning Monochromatization Crystal monochromators – LiF, SiO 2, 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° Monochromatization Crystal monochromators – LiF, SiO 2, 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 Monochromatization Monochromator shape usually flat – problems with divergent beams concentrating type – increases I by factor of 1.5-2


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