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Nuclear and Radiation Physics, BAU, 1 st Semester, 2006-2007 (Saed Dababneh). 1 Neutron-induced Reactions X ( n,b ) Y n ( E n ) b ( Q + E n ) For thermal.

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Presentation on theme: "Nuclear and Radiation Physics, BAU, 1 st Semester, 2006-2007 (Saed Dababneh). 1 Neutron-induced Reactions X ( n,b ) Y n ( E n ) b ( Q + E n ) For thermal."— Presentation transcript:

1 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 1 Neutron-induced Reactions X ( n,b ) Y n ( E n ) b ( Q + E n ) For thermal neutrons Q >> E n b ( Q ) constant Probability to penetrate the potential barrier P o ( E thermal ) = 1 P > o ( E thermal ) = 0 Non-resonant

2 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 2 Neutron-induced Reactions

3 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 3

4 4 Neutron-induced Reactionsn-TOFCERN

5 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 5

6 6 Neutron-induced Reactionsn_TOFCERN

7 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 7 Neutron-induced Reactions

8 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 8 Nuclear Radius Charged Particle Reactions What is the Gamow Peak?

9 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 9 Charged Particle Reactions Electron Screening

10 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 10 Charged Particle Reactions e 2 = 1.44x keV.m Tunneling probability: In numerical units: For -ray emission: Sommerfeld parameter Gamow factor Multipolarity

11 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 11 Charged Particle Reactions Nuclear (or astrophysical) S -factor

12 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 12 Charged Particle Reactions E C = ??

13 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 13 Resonance Reactions E t CN particle emission E E > spacing between virtual states continuum. (Lower part larger spacing isolated resonances). D bound states -emission E isolated states.

14 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 14 Resonance Reactions Entrance Channel a + X Exit Channel b + Y Compound Nucleus C* Excited State ExEx J a + X Y + bQ > 0 b + Y X + aQ < 0 Inverse Reaction QM Statistical Factor ( ) Identical particles Nature of force(s). Time-reversal invariance. HW 30

15 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 15 Resonance Reactions Projectile Target Q-value Projectile Q-value Target Direct Capture (all energies) Resonant Capture (selected energies with large X-section) E = E + Q - E ex Q + E R = E r

16 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 16

17 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 17 Resonance Reactions HW 31

18 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 18 Resonance Reactions Damped Oscillator eigenfrequency Damping factor Oscillator strength

19 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 19 Resonance Reactions Breit-Wigner formula All quantities in CM system Only for isolated resonances. Reaction Elastic scattering HW 32 HW 32 When does R take its maximum value? Usually a >> b.

20 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 20 Resonance Reactions J a + J X + l = J (-1) l (J a ) (J X ) = (J) (-1) l = (J) Natural parity. Exit Channel b + Y Compound Nucleus C* Excited State ExEx J Entrance Channel a + X

21 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 21 Cross section ECEC a Energy What is the Resonance Strength …? What is its significance? In what units is it measured? Resonance Reactions Charged particle radiative capture ( a, ) (What about neutrons?)

22 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 22 Resonance Reactions 14 N(p, ) Q = ?? E C = ?? E R = 2.0 MeV Formation via s -wave protons, J = ½, p = 0.1 MeV, dipole radiation E = 9.3 MeV, = 1 eV. Show that = 0.33 eV. If same resonance but at E R = 10 keV p = ?? E = ?? = ?? Show that = 3.3x eV. HW 33 Huge challenge to experimentalists

23 Nuclear and Radiation Physics, BAU, 1 st Semester, (Saed Dababneh). 23 Resonance J Estimated Energy (keV) ( eV) Experimental upper limit < 1.7 eV -transfer reactions Angular distribution 18 O(, ) 22 Ne


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