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Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). 1 Nuclear Reactions Categorization of Nuclear Reactions According to: bombarding particle, bombarding energy, target, reaction product, reaction mechanism. Bombarding particle: Charged particle reactions. [ (p,n) (p, ) (, ) heavy ion reactions ]. Neutron reactions. [ (n, ) (n,p) ….. ]. Photonuclear reactions. [ (,n) (,p) … ]. Electron induced reactions…………. Bombarding energy: Thermal. Epithermal. Slow. Fast. Low energy charged particles. High energy charged particles. Neutrons. ?

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Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). 2 Nuclear Reactions Targets: Light nuclei (A < 40). Medium weight nuclei (40 < A < 150). Heavy nuclei (A > 150). Reaction products: Scattering. Elastic 14 N(p,p) 14 N Inelastic 14 N(p,p / ) 14 N* Radiative capture. Fission and fusion. Spallation. ….. Reaction mechanism: Direct reactions. Compound nucleus reactions. More in what follows …. What is a transfer reaction….????? Stripping Pickup Resonant Non-resonant

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Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). 3 Reaction Cross Section(s) (Introduction) Probability. Projectile a will more probably hit target X if area is larger. Classically: = (R a + R X ) 2. Classical = ??? (in b) 1 H + 1 H, 1 H U, 238 U U Quantum mechanically: = 2. Coulomb and centrifugal barriers energy dependence of. Nature of force: Strong: 15 N(p, ) 12 C = 0.5 b at E p = 2 MeV. Electromagnetic: 3 He(, ) 7 Be = b at E = 2 MeV. Weak: p(p,e + )D = b at E p = 2 MeV. Experimental challenges to measure low X-sections.. HW 33

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Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). 4 Reaction Cross Section(s) (Introduction) d, IaIa Detector for particle b X target Nuclei / cm 2 a particles / s b particles / s cm 2 Typical nucleus (R=6 fm): geometrical R 2 1 b. Typical : 10 6 b.

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Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). 5 Reaction Cross Section(s) (Introduction) Many different quantities are called cross section. Krane Table 11.1 Angular distribution Differential cross section (, ) or ( ) or cross section …!! Units … ! Doubly differential Energy state in Y t for all b particles.

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Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). 6 Coulomb Scattering b d r min vovo v min Elastic or inelastic. Elastic Rutherford scattering. At any distance: V = 0 T a = ½mv o 2 l = mv o b No dependence on

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Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). 7 Coulomb Scattering

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Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). 8 Coulomb Scattering n target nuclei / cm 3 x target thickness (thin). nx target nuclei / cm 2 b db d b HW 34 Show that and hence Rutherford cross section

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Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). 9 Coulomb Scattering Study Fig (a,b,c,d) in Krane HW 35 Show that the fraction of incident alpha particles scattered at backward angles from a 2 m gold foil is 7.48x See also Fig in Krane.

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Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). 10 Coulomb Scattering Elastic Rutherford scattering. Inelastic Coulomb excitation. See the corresponding alpha spectrum of Fig in Krane.

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Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). 11 Coulomb Scattering

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Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). 12 Nuclear Scattering Elastic or inelastic. Analogous to diffraction. Alternating maxima and minima. First maximum at Minimum not at zero (sharp edge of the nucleus??) Clear for neutrons. Protons? High energy, large angles. Why? Inelastic Excited states, energy, X-section and spin-parity.

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