Mean-energy neutron moderation count
= Mean-energy neutron moderation count
{title2=$n=\log(E_f/E_i)/\log f$}
If every step retains the same conditional mean fraction $f$ of the incident kinetic energy, the mean after $n$ steps is $f^nE_i$. Solving for a target mean energy gives the displayed count. It describes an ensemble mean, not a guaranteed collision number for each neutron; averaging the logarithmic loss is another statistical convention.