Definition of cross sections 1 - Moodle

Definition of cross sections 61. Each type of nuclear reaction is characterized by a specific microscopic cross sectionσ x which is also function of the type of nuclide and on the velocity or kinetic energy ofthe neutron. However, the potential cross section is independent of neutron energy.2. An elastic neutron-nucleus collision is characterized by an elastic scattering crosssection σ e . This reaction includes both potential and resonant elastic collisions.3. The symbol Q represents the energy produced by a nuclear reaction in the form ofkinetic energy. In a threshold reactions, Q is negative and the nuclear reaction canoccur only if e exc ≥ −Q. If a scattering reaction has a threshold energy −Q, thecompound nucleus is left excited after the collision and decay with gamma rayemission of energy −Q (short half life). This is the inelastic scattering cross section(σ in ).The scattering cross section σ s is written σ s = σ e +σ in + ∑ x≥2 σ n,xn.σtotalσsσe σin σn,2n σ n,3n σfσγσασpscattering(n,xn)absorptiontransmutationENE6101: Week 4 Cross sections – 8/37