Definition of cross sections 1 - Moodle

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Content (week 4) 1Definition of cross sectionsFormation of a compound nucleusselection rulesresonancesPorter and Thomas distributionWigner distributionThe single level Breit-Wigner (SLBW) formularesonance parameters of 232 Th235 U, 238 U and 239 Pu cross sectionslow-energy variation of cross sectionsENE6101: Week 4 Cross sections – 2/37
Definition of cross sections 11. The trajectory of a neutron in a material is a straight line which can be interrupted by anuclear interaction with a nucleus of the material.2. The neutron-nucleus collision can result in a variety of nuclear reactions (such as theelastic scattering reaction).3. The concept of cross section is used to describe the probability of each type of nuclearreaction. The probability for a neutron located at r and moving in a material at velocityV n to undergo a nuclear reaction in a differential element of trajectory ds isindependent of the past history of the neutron and is proportional to ds.Let’s consider a one-speed and parallel beam of neutrons of intensity I neutrons per unitsurface and unit time. The beam hits perpendicularly a target of width ds. The targetcontains a unique type of nuclide with a number density of N nuclei per unit volume.I (cm-2 s-1)N (cm-3)ENE6101: Week 4 Cross sections – 3/37ds
Page 1: Cross sectionsAlain Hébertalain.he
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 and 12: Formation of a compound nucleus 2Ty
Page 13 and 14: Formation of a compound nucleus 4A
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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