Radiation Detection and Measurement, JU, 1st Semester, 2008-2009 Saed Dababneh 1 Nuclear Reaction Energetics Conservation Laws • Charge, Baryon number, total energy, linear momentum, angular momentum, parity, (isospin??) ……. a p a X p Y p b Y b Q T T c m c m i f f i 2 2 +ve Q-value exoergic reaction. -ve Q-value endoergic reaction. a Y b T Q T T +ve Q-value reaction possible if T a 0. -ve Q-value reaction not possible if T a 0. (Is T a > |Q| sufficient?). Conservation of momentum ……
Nuclear Reaction Energetics. Conservation Laws Charge, Baryon number , total energy, linear momentum, angular momentum, parity, ( isospin ??) ……. b. p b. . gs. a. p a. X. . +ve Q -value exoergic reaction. -ve Q -value endoergic reaction. p Y. Y. Stationary X ??. - PowerPoint PPT Presentation
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Radiation Detection and Measurement, JU, 1st Semester, 2008-2009 Saed Dababneh
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Nuclear Reaction Energetics
Conservation Laws• Charge, Baryon number, total energy, linear momentum, angular momentum, parity, (isospin??) …….
Threshold?o Elastic scattering (n,n). Q = ?? (Potential and CN).
Neutron moderation?o Radiative capture (n,). Q = ?? Capture gammas.o (n,), (n,p). Q = ?? Absorption Reactions.o (n,2n), (n,3n) Q = ?? Energetic neutrons on heavy water can easily eject the loosely bound neutron.o Fission. (n,f).
HW b2HW b2 Examples of such exo- and endo-thermic reactions with Q calculations.
Radiation Detection and Measurement, JU, 1st Semester, 2008-2009 Saed Dababneh
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Radiation Detection and Measurement, JU, 1st Semester, 2008-2009 Saed Dababneh
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n-TOFn-TOFCERNCERN
Radiation Detection and Measurement, JU, 1st Semester, 2008-2009 Saed Dababneh
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Radiation Detection and Measurement, JU, 1st Semester, 2008-2009 Saed Dababneh
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• Probability.• Projectile a will more probably hit target X if area is larger.• Classically: = (Ra + RX)2. Classical = ??? (in b) n + 1H, n + 238U, 238U + 238U • Quantum mechanically: = 2.
• Coulomb and centrifugal barriers energy dependence of . What about neutrons?What about neutrons?
CMaXaXaaX
Xa
EEmm
mm
22
Reaction Cross Section
Radiation Detection and Measurement, JU, 1st Semester, 2008-2009 Saed Dababneh
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Neutron Induced Reactions
22 nXHCCHbY IIIn X(n,b)Y
n(En)b(Q+En)
For thermal neutronsQ >> En
b(Q) constant
2
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vE
)( nln EPvn
Probability to penetrate the potential barrier
Po(Ethermal) = 1P>o(Ethermal) = 0
vEnn
1)( Non-resonant
Radiation Detection and Measurement, JU, 1st Semester, 2008-2009 Saed Dababneh