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Radiation interaction with matter

1. Radiation interaction with matter. 2. Outline. Introduction Generalities cross section dE/dx LET and NIEL Proton electrons range, practical range Ionising and non ionising dose Conclusion. 3. Particles of interest. protons [1MeV, 1GeV]. electrons [10keV, 10 MeV]. h n.

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Radiation interaction with matter

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  1. 1 Radiation interaction with matter

  2. 2 Outline • Introduction • Generalities • cross section • dE/dx • LET and NIEL • Proton • electrons • range, practical range • Ionising and non ionising dose • Conclusion

  3. 3 Particles of interest • protons • [1MeV, 1GeV] • electrons • [10keV, 10 MeV] hn • Photons • x, g • ions • [1 MeV/uma, 1 GeV/uma]

  4. dx dE E - dE E dx dE Interaction 4 GENERAL : Energy loss by unit path length Assuming a straight line trajectory

  5. 7 Incident particle Incident particle Nature of the medium silicium e- e- e- e- Slowing down Slowing down e- e- e- Si Si Si e- Si v • Electrons act as a viscous medium that slow down incident particle • In addition, the probability to encounter a nuclei is not nul e- e- e- e- e- e- e- Si e- Si e- Si Si e- Si v e- e- e- e- e- e- e- e- e- Si Si e- e- Si Si v e- e- e- e- Nuclear Reaction Coulombic Scattering 5,4 A 0,9 A a) b)

  6. 8 Ionisation and Displacement for charged particles • interaction with electrons • - ionisation • - Coulombic inelastic • scattering • interaction with nuclei • - displacements • - elastic scattering • - nuclear reaction interstitial vacancy

  7. 9 Total stopping power nucleus e- Bremsstrahlung Not negligeable for energetic electron in heavy material NIEL + phonon Ionising stopping power Not negligeable for low energy protons

  8. 12 • Proton stopping power • Unit : MeV/mm or MeV/mg.cm2 slowing down of particles dE/dx is proportional to density dE/dx is maximal when incident & target particle are identical r

  9. 13 • Stopping power of electrons slowing down of particles dE/dx is proportional to specific gravity dE/dx is maximal when incident & target particle are identical r

  10. P 14 Displacement damages vacancy interstitial

  11. P P Slowing down by ionisation 21 Protons Nuclear reaction E 10 MeV 1MeV displacement 0,1 MeV Elastic scattering - Coulombic scattering - nuclear scattering 188 eV In silicon No more displacement Recoil energy < 25 eV 1 eV

  12. Slowing down by ionisation 22 Interaction of Charged particles with matter : electrons E g - rays emission Bremsstrahlung Gamma 1MeV Some displacements - Coulombic scattering 250 keV In silicon No more displacement Recoil energy < 25 eV

  13. g - rays E l 1MeV 1 pm 10 nm 100eV Gamma ray emission by interaction with electric field of the atom of the target Zincident Ztarget 400 nm 3eV 750 nm 1eV 2 1 mm 10-3 eV I a Mincident m 23 Bremsstrahlung : Interaction of electromagnetic radiation with matter Proton Electron • negligeable • large Mincident • Heavy material • with large Ztarget

  14. Al 27 Al 13 Material surface 1 MeV electron beam 24 Range of particles • The range is deduced from the stopping power Range > depth depth Mean penetration depth range

  15. 25 Range of protons & ions Protons in different materials Ions in silicon

  16. 26 Range of electrons

  17. 27 Order of magnitude

  18. Aluminium Proton (100 MeV) Aluminium Electrons (1 MeV) Back-scattered electron 28 trajectories 100 MeV protons in Al 10 MeV electrons in AlBremsstrahlung 84 MeV Carbon in Silicon1 MeV electrons in Al

  19. dx h atoms/cm3 Surface S Incident Number of particle dna scattered particles F. NIEL Flux F Deposited energy DE Volume Mass 29 Ionising and non ionising dose Dose is the averaged energy deposited by unit of mass : J/ kg = Gray 1 Gray = 100 rad

  20. 30 Ionising Dose : Normaly incident protons Due to straggling and scattering Compromise between the increase of the LET and the decrease of the flux due to scattering

  21. Material surface Al 27 Al 13 31 Ionising Dose : Normaly incident electrons Peack smoother than for protons as electrons are largely scattered

  22. 32 Ionising Dose : Normaly incident electrons + Bremsstrahlung Bragg Peak Dose enhancement gamma

  23. 33 Mission ionising dose : LEO, GEO

  24. 34 Mission ionising dose : GPS

  25. 37 Conclusion Electron act as a viscous medium that slow down incident charged particles Interaction with electron produce ionisation (LET) Interaction with nuclei produce displacement (NIEL) Ionising and non ionising dose (Energy deposited by unit of mass)

  26. 38 Conclusion LET is used to quantify SEE effects (sSEU(LET)) NIEL is used to quantify degradation of optoelectronic components Dose is used to quantify degradation of electronic devices ( MOS, Bipolar) LET, NIEL and dose are the fondemental parameters used to quantify many degradations induced by space radiations

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