The Placzek transient is a phenomenon studied in nuclear engineering.
The Placzek transient occurs when a population of monoenergetic neutrons of energy E elastically scatter within a homogeneous medium.
The transient results from the fact that after the 1st generation, every neutron can have at minimum an energy of
Thus, the discontinuity in the flux arises from the fact that at each multiple of
The Placzek transient can be derived analytically by solving for the neutron flux using a piecewise function solution to a differential equation involving a Heaviside step function in energy intervals of width
The transient can also be observed in some special case Monte Carlo neutron transport simulation codes.