**Nuclear Reactions** Sample Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Nuclear Reactions** Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Nuclear Reactions** Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Nuclear Reactions** Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Nuclear Reactions** • If the reaction reaches excited states of Y 58Ni(,p)61Cu even less …. less proton energy Highest proton energy See Figures 11.4 in Krane Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Nuclear Reactions** • Neutron scattering • Inelastic Q = -Eex (=-E*). • Elastic Q = 0. HW 32 Discuss the elastic and inelastic scattering of neutrons using the relations you derived in HW 31. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**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. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Nuclear Reactions** • Targets: • Light nuclei (A < 40). • Medium weight nuclei (40 < A < 150). • Heavy nuclei (A > 150). • Reaction products: • Scattering. Elastic 14N(p,p)14N Inelastic 14N(p,p/)14N* • Radiative capture. • Fission and fusion. • Spallation. • ….. • Reaction mechanism: • Direct reactions. • Compound nucleus reactions. • More in what follows …. • What is a transfer reaction….????? Pickup Resonant Stripping Non-resonant Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Reaction Cross Section(s) (Introduction)** • Probability. • Projectile a will more probably hit target X if area is larger. • Classically: = (Ra + RX)2. • Classical = ??? (in b)1H + 1H, 1H + 238U, 238U + 238U • Quantum mechanically: = 2. • Coulomb and centrifugal barriers energy dependence of . • Nature of force: • Strong: 15N(p,)12C = 0.5 b at Ep = 2 MeV. • Electromagnetic: 3He(,)7Be = 10-6 b at E = 2 MeV. • Weak: p(p,e+)D = 10-20 b at Ep = 2 MeV. • Experimental challenges to measure low X-sections.. HW 33 Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Reaction Cross Section(s) (Introduction)** Detector for particle “b” d Ia “b” particles / s , cm2 “X“ target Nuclei / cm2 “a” particles / s Typical nucleus (R=6 fm): geometrical R2 1 b. Typical : <b to >106 b. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Reaction Cross Section(s) (Introduction)** Many different quantities are called “cross section”. Krane Table 11.1 Angular distribution Units … ! “Differential” cross section (,) or ( ) or “cross section” …!! Doubly differential t for all “b” particles. Energy state in “Y” Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Coulomb Scattering** • Elastic or inelastic. • Elastic Rutherford scattering. • At any distance: V = 0 Ta = ½mvo2 l = mvob vmin vo rmin b d Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh). No dependence on

**Coulomb Scattering** Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Coulomb Scattering** b < b > dbd n target nuclei / cm3 x target thickness (thin). nx target nuclei / cm2 HW 34 Show that and hence b Rutherford cross section Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Coulomb Scattering** Study Fig. 11.10 (a,b,c,d) in Krane See also Fig. 11.11 in Krane. HW 35 Show that the fraction of incident alpha particles scattered at backward angles from a 2 m gold foil is 7.48x10-5. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Coulomb Scattering** • Elastic Rutherford scattering. • Inelastic Coulomb excitation. See the corresponding alpha spectrum of Fig. 11.12 in Krane. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**Coulomb Scattering** Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

**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. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).