The confinement of a high-pressure plasma in a multi-mirror magnetic configuration with a corrugated metal casing is studied analytically and numerically. Equations are derived describing the dynamics of a dense plasma in a corrugated magnetic field and it is shown that the structure of the magnetic lines of force is maintained during transverse expansion of a hot plasma. The energy confinement time is found to be of the order of R2/χ under the assumption that the thermal diffusivity χ is Bohm-like.