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INTERACTIONS OF IONIZING RADIATION WITH MATTERS

INTERACTIONS OF IONIZING RADIATION WITH MATTERS. DR. CHAU VAN TAO DEPARTMENT OF NUCLEAR PHYSICS NATURALSCIENCES UNIVERSITY. Questions. What is radiation? What is ‘ionizing’ radiation? How do we measure radiation? Where does radiation come from? What are the effects of radiation?

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INTERACTIONS OF IONIZING RADIATION WITH MATTERS

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  1. INTERACTIONS OF IONIZING RADIATION WITH MATTERS DR. CHAU VAN TAO DEPARTMENT OF NUCLEAR PHYSICS NATURALSCIENCES UNIVERSITY

  2. Questions • What is radiation? • What is ‘ionizing’ radiation? • How do we measure radiation? • Where does radiation come from? • What are the effects of radiation? • Is radiation good for anything?

  3. Atomic Structure and Radioactive Decay Atomic Structure electron nucleus proton neutron

  4. Discovery of Radiation Discovery of Radiation Pierre & Marie Curie 1898 Discovery ofRa, Po Röntgen 1895 Discovery of X-ray Hahn 1938 Discovery of fission Becquerel 1896 Spontaneous radioactivity

  5. Types of Radiation and Nuclear Energy Ernest Rutherford(1871-1935) Albert Einstein(1879- 1955)

  6. Atomic Structure and Radioactive Decay Atoms and Isotopes A Z XN X-A or 4 2 He He-4 X: Chemical Symbol A: Atomic mass number Z: Atomic number N: Neutron number A=Z+N 422

  7. Atomic Structure and Radioactive Decay b-decay and g-ray emission b g electromagnetic radiation electron Co-60 Proton : 27 Neutron: 33 Ni-60* Proton : 28 Neutron: 32 Ni-60 Proton : 28 Neutron: 32

  8. + + + - + electron + More Radioactivity Antoine Henri Becquerel (1852—1908) Gamma ray 7Be  7Li +  7Be Positron 11C 11C  11B + + Beta ray (electron) 60Co 60Co  60Ni + – Discovered radioactivity of uranium Alpha ray (helium nucleus) 226Ra 226Ra  222Rn + 

  9. Atomic Structure and Radioactive Decay a-decay proton neutron a nucleus U-238 Proton : 92 Neutron: 146 Th-234 Proton : 90 Neutron: 144

  10. Types of Radiation Types of Radiation a, b,g-ray Lead block b-ray g-ray a-ray (+) (-) Electrically charged plates Photographic plate Radioactive substance

  11. Types of Radiation Types of Radiation

  12. Characteristics of Radiation Half-life Time of Radionuclide l: Probability of disintegration per unit time • A = A0e-lt • Half Life,Ｔ1/2 = log2 / l

  13. Characteristics of Radiation Half-life Time of Radionuclide

  14. Characteristics of Radiation Penetrating Distances Paper Plastic Lead Concrete Skin Aluminum Iron Water a b g and X neutron

  15. BUT: Radiation can also be interpreted as particles (photons) with energy E Speed of light E = hf Planck’s constant Electromagnetic Radiation f = c/

  16. + + + + ‘Ionizing’ Radiation - Electron Radiation - Ion Radiation that is energetic enough to remove a tightly bound electron from a neutral atom

  17. + + + + + + + + + + + + + + + + + + + + + + + + ‘Ionizing’ Radiation a b Different kinds of radiation produce different patterns of ionization

  18. Electromagnetic Spectrum Non ionizing Ionizing

  19. A A Measuring Radiation (Ion Chamber)

  20. Measuring Radiation (Geiger Counter) Geiger–Müller Tube

  21. 256 16 1 4 64 Measuring Radiation (Scintillator) Dynodes Light guide Scintillator 4096… 410 = 1,048,576 Electrical pulse 1024… Photomultiplier tube Photocathode

  22. The Gamma Spectrometer

  23. Lesson 1 - Inverse Square Law of Gamma Radiation I0 I0 I1 x1

  24. I0 I1 I2 x2

  25. logk-2logx mm mm

  26. Lesson 2 –The Decrease Of Gamma Intensity Io

  27. Interaction of Radiation with Matter Interaction ofElectromagnetic Radiation with Matter Photoelectric Effect e- g-ray photoelectron

  28. Interaction of Radiation with Matter Interaction ofElectromagnetic Radiation with Matter Compton Scattering g1’-ray g-ray e- electron E:  energy of the incident photon Es:  energy of the scattered photon q :  the scattering angle m:  electron mass

  29. Interaction of Radiation with Matter Interaction ofElectromagnetic Radiation with Matter Pair Production e+ positron g-ray e- E  =  2mc2 + E+ + E- electron m:  electron rest mass c:  the speed of light E+:  kinetic energies of the positron E-:  kinetic energy of the electron

  30. Interaction of Radiation with Matter µ Photoelectric Effect Compton Scattering Pair Production

  31. -x mm mm

  32. Lesson 3 - The Gamma Spectrum b g electromagnetic radiation electron Co-60 Proton : 27 Neutron: 33 Ni-60* Proton : 28 Neutron: 32 Ni-60 Proton : 28 Neutron: 32

  33. Lesson 3 - The Gamma Spectrum  

  34. Cobalt Spectrum

  35. THANK YOU FOR ATTENTION

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