  We report the presence of scattered light from dust grains located in the
giant planet formation region of the circumbinary disk orbiting the ~20-Myr-old
close (~0.045 AU separation) binary system V4046 Sgr AB based on observations
with the new Gemini Planet Imager (GPI) instrument. These GPI images probe to
within ~7 AU of the central binary with linear spatial resolution of ~3 AU, and
are thereby capable of revealing dust disk structure within a region
corresponding to the giant planets in our solar system. The GPI imaging reveals
a relatively narrow (FWHM ~10 AU) ring of polarized near-infrared flux whose
brightness peaks at ~14 AU. This ~14 AU radius ring is surrounded by a fainter
outer halo of scattered light extending to ~45 AU, which coincides with
previously detected mm-wave thermal dust emission. The presence of small grains
that efficiently scatter starlight well inside the mm-wavelength disk cavity
supports current models of planet formation that suggest planet-disk
interactions can generate pressure traps that impose strong radial variations
in the particle size distribution throughout the disk.
