  Galactic cosmic rays are believed to be accelerated at supernova remnants.
However, whether supernova remnants can be Pevatrons is still very unclear. In
this work we argue that PeV cosmic rays can be accelerated during the early
phase of a supernova blast wave expansion in dense red supergiant winds. We
solve in spherical geometry a system combining a diffusive-convection equation
which treats cosmic-ray dynamics coupled to magnetohydrodynamics to follow gas
dynamics. The fast shock expanding in a dense ionized wind is able to trigger
the fast non-resonant streaming instability over day timescales, and energizes
cosmic-rays even under the effect of p-p losses. We find that such environments
make the blast wave a Pevatron, although the maximum energy depends on various
parameters such as the injection rate and mass-loss rate of the winds.
Multi-PeV energies can be reached if the progenitor mass loss rates are of the
order of $10^{-3}$ Msun yr$^{-1}$. It has been recently invoked that, prior to
the explosion, hydrogen rich massive stars can produce enhanced mass loss
rates. These enhanced rates would then favor the production of a Pevatron phase
in early times after the shock breakout.
