Definition of cross sections 1 - Moodle

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Formation of a compound nucleus 3≈ 1 eV2J π 2(excited level)eexces = –Q14AZXI π 1negative resonances3Sn(A+1,Z)≈ 5 MeV≈ 40 keVA+1Z X (compound nucleus)ENE6101: Week 4 Cross sections – 12/37
Formation of a compound nucleus 4A decay channel is open only if the three following laws are observed: conservation ofenergy, linear and angular momentum of the nuclide-nucleus pair. The first two laws havealready been studied in Week 3. The conservation of angular momentum is written(12)J = I +K +L whereI , K = angular momentum of the target nucleus A ZX in its ground state and of the neutronJ = angular momentum of the compound nucleus A+1ZX in its excited stateL = orbital angular momentum of the nuclide-nucleus pair in the CM.The classical definition of the orbital angular momentum of the nuclide-nucleus pair aboutthe origin of the CM is L = m(r n −r CM )×v n +mA(r A −r CM )×v A .Using relations in week 3 and defining the e z –directed axis as perpendicular to the planewhere the particles are moving, this equation simplifies to(13)L = ∆RV R m 0 e zwhere ∆R is the distance between the lines of definition of vectors v n and v A in the CM andm 0 is the reduced mass of the neutron defined as m 0 = mAA+1 .ENE6101: Week 4 Cross sections – 13/37
Page 1 and 2: Cross sectionsAlain Hébertalain.he
Page 3 and 4: Definition of cross sections 11. Th
Page 5 and 6: Definition of cross sections 3The m
Page 7 and 8: Definition of cross sections 5The r
Page 9 and 10: Definition of cross sections 7In a
Page 11: Formation of a compound nucleus 2Ty
Page 15 and 16: Selection rules 1The parity π is a
Page 17 and 18: Resonances 21. Each excitation leve
Page 19 and 20: Resonances 4The first three values
Page 21 and 22: Porter and Thomas distribution 1P(x
Page 23 and 24: Wigner distribution 1S(x)0.80.70.60
Page 25 and 26: The SLBW formula 2The parameter σ
Page 27 and 28: The SLBW formula 4The first values
Page 29 and 30: The SLBW formula 6This is a very we
Page 31 and 32: The SLBW formula 8The SLBW equation
Page 33 and 34: Uranium-235 total cross section 1Mi
Page 35 and 36: Plutonium-239 total cross section 1
Page 37: Low-energy variation of cross secti

Definition of cross sections 1 - Moodle

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