  Simulations using 3D and 2D full-wave codes have shown that edge filaments in
tokamak plasmas can significantly affect the propagation of microwaves across a
broad frequency spectrum, resulting in scattering angles of up to 46 degrees.
Parameter scans were carried out for density perturbations comparable in width
and amplitude to MAST filaments and the effect on the measured emission was
calculated. 3D effects were discovered in the case of an obliquely incident
beam.
  In general, the problem of EM propagation past wavelength-sized 3D
inhomogeneities is not well understood, yet is of importance for both heating
and diagnostic applications in the electron cyclotron frequency range for
tokamaks, as well as atmospheric physics. To improve this understanding, a new
cold-plasma code, EMIT-3D, was written to extend full-wave microwave
simulations in magnetized plasmas to 3D, and make comparisons to the existing
2D code IPF-FDMC. This work supports MAST experiments using the SAMI diagnostic
to image microwave emission from the plasma edge due to mode conversion from
electron Bernstein waves. Significant fluctuations in the SAMI data mean that
detailed modelling is required to improve its interpretation.
