  Negative triangularity (NT) tokamak configurations may be more susceptible to
magneto-hydrodynamic instability, posing challenges for recent reactor designs
centered around their favorable properties, such as improved confinement and
operation free of edge-localized modes. In this work, we assess the vertical
stability of plasmas with NT shaping and develop potential reactor solutions.
When coupled with a conformal wall, NT equilibria are confirmed to be less
vertically stable than equivalent positive triangularity (PT) configurations.
Unlike PT, their vertical stability is degraded at higher poloidal beta.
Furthermore, improvements in vertical stability at low aspect ratio do not
translate to the NT geometry. NT equilibria are stabilized in PT vacuum vessels
due to the increased proximity of the plasma and the wall on the outboard side,
but this scenario is found to be undesirable due to reduced vertical gaps which
give less spatial margin for control recovery. Instead, we demonstrate that
informed positioning of passively conducting plates can lead to improved
vertical stability in NT configurations on par with stability metrics expected
in PT scenarios. An optimal setup for passive plates in highly elongated NT
devices is presented, where plates on the outboard side of the device reduce
vertical instability growth rates to 16% of their baseline value. For lower
target elongations, integration of passive stabilizers with divertor concepts
can lead to significant improvements in vertical stability. Plates on the
inboard side of the device are also uniquely enabled in NT geometries,
providing opportunity for spatial separation of vertical stability coils and
passive stabilizers.
