Secondary emission (SE) refers to the emission of particles from a surface as a result of the impact of a particle. Analyst uses a stochastic SE model developed by Furman and Pivi in which an impact produces 0 or more secondary particles whose count, directions, and energies are obtained by sampling a set of random variables. Secondary particles are generally binned into two categories: backscattered (including reflected and re-diffused primaries), and true secondaries. The physical processes that lead to each category are different, and the Furman-Pivi model treats each one separately while still imposing the necessary energy and current constraints on the collective process.
There are a number of parameters that are used to control the SE model, with the most important being the values that control the true secondary yield. True secondaries are generated only by relatively low-energy impacts, and an impact can produce several secondary particles under the right conditions. Consequently, true secondary emission is typically the dominant process in most multipacting phenomena. The default true secondary model has the following form:
where is the normalized impact energy. Parameters , , and are set to produce the desired yield curve.