  The exoplanetary system of HR 8799 is one of the rare systems in which
multiple planets have been directly imaged. Its architecture is strikingly
similar to that of the Solar System, with the four imaged giant planets
surrounding a warm dust belt analogous to the Asteroid Belt, and themselves
being surrounded by a cold dust belt analogue to the Kuiper Belt. Previous
observations of this cold belt with ALMA in Band 6 (1.3 mm) revealed its inner
edge, but analyses of the data differ on its precise location. It was therefore
unclear whether the outermost planet HR 8799 b was dynamically sculpting it or
not. We present here new ALMA observations of this debris disk in Band 7 (340
GHz, 880 micron). These are the most detailed observations of this disk
obtained so far, with a resolution of 1" (40 au) and sensitivity of
$9.8\,\mu\mathrm{Jy\,beam^{-1}}$, which allowed us to recover the disk
structure with high confidence. In order to constrain the disk morphology, we
fit its emission using radiative transfer models combined with a MCMC
procedure. We find that this disk cannot be adequately represented by a single
power law with sharp edges. It exhibits a smoothly rising inner edge and
smoothly falling outer edge, with a peak in between, as expected from a disk
that contains a high eccentricity component, hence confirming previous
findings. Whether this excited population and inner edge shape stem from the
presence of an additional planet remains, however, an open question.
