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In nuclear physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. The neutron cross section σ can be defined as the area in cm 2 for which the number of neutron-nuclei reactions taking place is equal to the product of the number of incident neutrons that would pass through the area and the number of ...
Devices coated with natural Gd have also been explored, mainly because of its large thermal neutron microscopic cross section of 49,000 barns. [37] [38] However, the Gd(n,γ) reaction products of interest are mainly low energy conversion electrons, mostly grouped around 70 keV. Consequently, discrimination between neutron induced events and ...
The absorption neutron cross section of an isotope of a chemical element is the effective cross-sectional area that an atom of that isotope presents to absorption and is a measure of the probability of neutron capture. It is usually measured in barns. Absorption cross section is often highly dependent on neutron energy. In general, the ...
Nuclear cross sections are used in determining the nuclear reaction rate, and are governed by the reaction rate equation for a particular set of particles (usually viewed as a "beam and target" thought experiment where one particle or nucleus is the "target", which is typically at rest, and the other is treated as a "beam", which is a projectile with a given energy).
Cross sections can be computed for atomic collisions but also are used in the subatomic realm. For example, in nuclear physics a "gas" of low-energy neutrons collides with nuclei in a reactor or other nuclear device, with a cross section that is energy-dependent and hence also with well-defined mean free path between collisions.
Deterministic methods usually involve multi-group approaches while Monte Carlo can work with multi-group and continuous energy cross-section libraries. Multi-group calculations are usually iterative, because the group constants are calculated using flux-energy profiles, which are determined as the result of the neutron transport calculation.
Neutron spectroscopy is a spectroscopic method of measuring atomic and magnetic motions by measuring the kinetic energy of emitted neutrons. The measured neutrons may be emitted directly (for example, by nuclear reactions ), or they may scatter off cold matter before reaching the detector.
The absorption cross section for 10 B (top) and 11 B (bottom) as a function of energy Chemical elements with usefully high neutron capture cross-sections include silver , indium , and cadmium . Other candidate elements include boron , cobalt , hafnium , samarium , europium , gadolinium , terbium , dysprosium , holmium , erbium , thulium ...