  We have used the TOPAS simulation framework to model the direct conversion of
511 keV gamma rays to electrons in a micro-channel plate (MCP) constructed from
thin laminae of a heavy-metal-loaded dielectric such as lead-glass, patterned
with micro-channels (LMCP). The laminae serve as the converter of the gamma ray
to a primary electron within a depth from a channel-forming surface such that
the electron penetrates the channel surface (`surface direct conversion'). The
channels are coated with a secondary-emitting material to produce electron
multiplication in the channels. The laminae are stacked on edge with the
channels running from the top of the resulting `slab' to the bottom; after
assembly the slab is metalized top and bottom to form the finished LMCP.
  The shape of the perimeter of a lamina determines the dimensions of the slab
at the lamina location in the slab, allowing non-uniform cross-sections in slab
thickness, width, and length. The slab also can be non-planar, allowing curved
surfaces in both lateral dimensions. The laminar construction allows
incorporating structural elements in the LMCP for modular assembly in
large-area arrays.
  The channels can be patterned on the laminae surfaces with internal shapes
and structure, texture, and coatings optimized for specific applications and
performance. The channels can be non-uniform across the LMCP and need not be
parallel in either transverse direction.
  Surface direct conversion of the gamma ray to an electron eliminates the
common two-step conversion of the gamma ray into an optical photon in a
scintillator followed by the conversion of the photon into an electron in a
photodetector. The simulations predict an efficiency for conversion of 511 keV
gamma rays of $\gtrapprox$ 30\% for a 2.54 cm-thick lead-glass LMCP. The
elimination of the photocathode allows assembly at atmospheric pressure.
