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NE 105 - Introduction to Nuclear Engineering Spring 2011

NE 105 - Introduction to Nuclear Engineering Spring 2011. Classroom Session 4 - Fundamental Concepts End Nuclear Energetics Intro Classic and Relativistic Calculations Photon Interactions with Matter Nuclear Energetics. Electron Volt.

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NE 105 - Introduction to Nuclear Engineering Spring 2011

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  1. NE 105 - Introduction to Nuclear EngineeringSpring 2011 Classroom Session 4 - Fundamental Concepts End Nuclear Energetics Intro Classic and Relativistic Calculations Photon Interactions with Matter Nuclear Energetics

  2. Electron Volt • Work done by one electron accelerated through a potential difference of one volt 1 eV = 1.60217646x10-19 J Example: What is the speed (m/s) of a 12 eV134Xe ion? (from the chart of the nuclides: 134Xe Weights = 133.905394 AMU) Use classic concept of KE for now amu in table 1.5 Joule = Energy, Work = Force (N) x d =kg m2/s2

  3. Correction of the book… REMEMBER! Book: Page 6 Please ignore the c2. It is confusing

  4. 4156.4 m/s ~9,300 m.p.hi.e. even very low energy ions are moving pretty fast • Please remember this is ONLY for classical calculations. • At energies close to “c”, need to use relativistic calculations

  5. What is the speed of a 100.00 MeVproton: • 102,540 m/s • 5,467 g/s • 1.38e8 m/s • 13840 m/s • 3e8 m/s

  6. What is the speed of a 100.00 MeV proton: 100MeV proton = 0.46 c :close to the speed of light. i.e. classic equations do NOT hold i.e. 0.46 is likely wrong

  7. Newton Laws • For over 200 years, Newton’s laws worked • Accurately described many physical behaviors • Unifying the earth and the skies • Previously: • Sub-lunar sphere: impure and imperfect • Skies: perfect and immutable (circle, ether)

  8. Special Theory of Relativity - Effects • “Mass Increase” with increasing velocity Increase quantified by Lorentz factor ():

  9. Special Theory of Relativity - Effects • Length and time are also modified relative to an object’s speed For example: To find speed…

  10. Special Theory of Relativity - Effects • What is the kinetic energy of a 100.00 MeVproton? Hint: Relativistic speeds, i.e. use this equation:

  11. The error grows as v  c

  12. Remember • Relativistic calculation required when: kinetic energy ~ rest energy • What is the rest mass of an electron? • What is the rest mass of a p+ or n0? • What is the rest mass of heavy ions? (Table 1.5 book) Use: eV keV MeV

  13. What is the kinetic energy of a 1 MeV electron?Rest mass of the electron, me=0.511MeV • 0.511 MeV • 0.489 MeV • 0.999 MeV • 1 MeV • 0 MeV

  14. What is the speed of a 1 MeV electron?Rest mass of the electron, me=0.511MeV • 0.58c • 0.81c • 0.86c • 0.94c • 0.993c

  15. Solution:

  16. Special Theory of Relativity - Effects In Nuclear Engineering we rarely work with neutrons of more than 10MeV. We stick to classic calculations for KE of p, n, , ions, and fission fragments Homework 2.3. What is the error in computing speed of a 10 MeV neutron classically instead of relativistically?

  17. Radiation Interaction with Matter Ionizing Radiation

  18. Photon Interactions High Low Intermediate Energy Compton Scattering Pair Production Photoelectric Effect

  19. Pair Production

  20. Compton Scattering

  21. The Photoelectric Effect

  22. Compton Scattering – The Experiment • In 1922, Compton obtained this data • Scattered X-Rays had an increasein wavelength • Can you explain why? E’ E

  23. Compton Scattering – Light has p! E’ Why the equation written for the photon angle? • If light is a wave, then radiation scattered by an electron should have no change in wavelength • In 1922, Compton demonstrated that that x-rays scattered from electrons had a decrease in wavelength. This is only possible if light is treated as a particle with linear momentum equal to p=h/ E

  24. Follow equations • But pay attention to units • For wavelength please use nm

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