how to set nonlinear interaction coefficient when two beam launch in nonlin medium

we are dealing with Rsoft Fullwave product. We are using two gaussian beams launch opposit to each other in a nonlinear medium.

we want to set the nonlinear interaction coefficient(kappa) for two beams which are propagating in a nonlinear media (cross phase modulation). For our application we have to set kappa equals to 1.

kindly help us to resolve this issue

with regards
sonu gupta

Not sure why but somehow I get the feeling you're talking about a railgun.

The internet has several websites describing experiments with railguns. At least one ought to have equations for what you want.

we are doing modelling/simulation with the help of commercial software Rsoft fullwave product.
so we want help on defining the cross-phase modulation(two beam propagation in nonlinear medium) term.
lets say input power of one beam is P and E for another beam. when these two beams propagates in a nonlinear medium then they will interect to each other and one beam effect to each other.
suppose the nonlinear coefficent is chi3, then nonlinear interation can be modelled as
Chi3* (P+K*)E..........where K is the interaction terms.
for our application we want to set the K=1. anybody have any idea to model this problem in Rsoft fullwave. kindly help