Control rods made from boron-10 or a silver-indium-cadmium alloy are used in nuclear reactors due to their high cross sections for the “capture” of these particles. For 10 points each:
[10e] Name these particles which are “moderated” by materials like water and graphite. Along with protons, these particles compose the nucleus of an atom.
ANSWER: neutrons [accept neutron moderation or neutron capture; prompt on n]
[10m] Neutron moderators may slow neutrons below the range of these phenomena. The Breit-Wigner formula may be used to compute cross-sections of these phenomena, which appear as peaks on scattering diagrams.
ANSWER: resonances
[10h] The thermal neutron cross section exhibits this dependence on the velocity v. This dependence may be derived from the Breit-Wigner distribution by assuming energies far below the resonance.
ANSWER: one over v [or one divided by v; or the reciprocal of v; or v to the power of minus one]
<JC, Physics>