PML (Perfectly Matched Layer) Implementation in the Magic Software

Abstract

Summary form only given. The PML (perfectly matched layer) boundary condition of Berenger, is implemented in the MAGIC finite-difference particle-in-cell software, and its behavior is verified and studied. This boundary condition provides a matched electric/magnetic absorber, in a tapered profile, similar to the software's existing "free-space" boundary condition, with the added promise of improved performance for all angles of incidence. We are most interested in aspects of the PML boundary condition's behavior in practical simulation situations, where such behavior may be less well known, despite the already widespread use of the PML. Of particular interest to particle-in-cell software is a manageable treatment of particle impact on the PML, since the PML can artificially grow a longitudinal wave, such as what would occur for particle current penetrating the layer. Also of primary interest is the use of a PML for a wide-band termination for waveguides. Three aspects of this problem are investigated: wide-band performance without need for tuning parameters, behavior near cutoff, and long duration stability in the presence of nearby or included structure, where fringe fields penetrate into the layer. The proper choice of profile for the absorbing material remains an active topic of research, as every PML implementation contains the apparent contradiction of requiring a smooth and gradual transition to the absorbing material, despite nominally being "perfectly matched", an attribute which is understood to be due to finite differencing effects, but remains less than well understood. Time permitting, we will also investigate such finite differencing effects, and possible mitigation strategies