Microscopic Versus Macroscopic Cross Section
Up to now, the cross section referred to in this article corresponds to the microscopic cross section σ. However, it is possible to define the macroscopic cross section Σ which corresponds to the total “equivalent area” of all target particles per unit volume:
where N is the atomic density of target.
Therefore, since the cross section can be expressed in cm2 and the density in cm−3, the macroscopic cross section is usually expressed in cm−1. Using equation derived in #Link to reaction rate and interpretation, the reaction rate per unit volume R can be derived using only the neutron flux Φ and the macroscopic cross section Σ:
Read more about this topic: Neutron Cross Section
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