Macroscopic nuclear reaction cross section
= Macroscopic nuclear reaction cross section
{title2=$\Sigma=\sum_iN_i\sigma_i$}
= Macroscopic cross section
{synonym}
A reaction coefficient formed from target <number densities> and microscopic <nuclear reaction cross-sections>. It has inverse-length units. Multiplying it by the scalar <neutron flux> gives the corresponding reaction rate per volume, under the stated energy averaging.