  The Summertime Line Intensity Mapper (SLIM) is a mm-wave line-intensity
mapping (mm-LIM) experiment for the South Pole Telescope (SPT). The goal of
SPT-SLIM is to serve as a technical and scientific pathfinder for the
demonstration of the suitability and in-field performance of multi-pixel
superconducting filterbank spectrometers for future mm-LIM experiments.
Scheduled to deploy in the 2023-24 austral summer, the SPT-SLIM focal plane
will include 18 dual-polarization pixels, each coupled to an $R =
\lambda/\Delta\lambda$ = 300 thin- film microstrip filterbank spectrometer that
spans the 2 mm atmospheric window (120-180 GHz). Each individual spectral
channel feeds a microstrip-coupled lumped-element kinetic inductance detector,
which provides the highly multiplexed readout for the 10k detectors needed for
SPT-SLIM. Here we present an overview of the preliminary design of key aspects
of the SPT-SLIM the focal plane array, a description of the detector
architecture and predicted performance, and initial test results that will be
used to inform the final design of the SPT- SLIM spectrometer array.
