  Fractal TRIDYN (F-TRIDYN) is a modified version of the widely used Monte
Carlo, Binary Collision Approximation code TRIDYN that includes an explicit
model of surface roughness and additional output modes for coupling to plasma
edge and material codes. Surface roughness plays an important role in ion
irradiation processes such as sputtering; roughness can significantly increase
the angle of maximum sputtering and change the maximum observed sputtering
yield by a factor of 2 or more. The complete effect of surface roughness on
sputtering and other ion irradiation phenomena is not completely understood.
Many rough surfaces can be consistently and realistically modeled by fractals,
using the fractal dimension and fractal length scale as the sole input
parameters. F-TRIDYN includes a robust fractal surface algorithm that is more
computationally efficient than those in previous fractal codes and which
reproduces available experimental sputtering data from rough surfaces. Fractals
provide a compelling path toward a complete and concise understanding of the
effect that surface geometry plays on the behavior of plasma-facing materials.
F-TRIDYN is a flexible code for simulating ion-solid interactions and coupling
to plasma and material codes for multiscale modeling.
