  We present a concept for an imaging gamma-ray polarimeter operating from ~50
MeV to ~1 GeV. Such an instrument would be valuable for the study of
high-energy pulsars, active galactic nuclei, supernova remnants, and gamma-ray
bursts. The concept makes use of pixelized gas micro-well detectors, under
development at Goddard Space Flight Center, to record the electron-positron
tracks from pair-production events in a large gas volume. Pixelized micro-well
detectors have the potential to form large-volume 3-D track imagers with ~100
micron (rms) position resolution at moderate cost. The combination of high
spatial resolution and a continuous low-density gas medium permits many
thousands of measurements per radiation length, allowing the particle tracks to
be imaged accurately before multiple scattering masks their original
directions. The polarization of the incoming radiation may then be determined
from the azimuthal distribution of the electron-positron pairs. We have
performed Geant4 simulations of these processes to estimate the polarization
sensitivity of a simple telescope geometry at 100 MeV.
