The paper discusses the radiation pressure dominated regime of relativistic ion acceleration, where ultra-intense electromagnetic waves interact with solid materials, transforming wave energy into the energy of ions. This regime, known as the "laser piston" (LP) regime, is highly efficient and can generate high-density ultra-short relativistic ion beams. The authors present a detailed analysis and three-dimensional particle-in-cell (PIC) simulations to support their findings. The LP regime involves two stages: (1) relativistic electron acceleration and charge separation, leading to relativistic ion energies, and (2) the accelerated foil acting as a plasma mirror, where the laser pulse is reflected, and the radiation pressure accelerates the ions further. The simulations show that the maximum ion energy can reach 30 GeV, with an efficiency of 30% for all ions. The authors suggest that this regime could be used in a laser-driven heavy ion collider, potentially enabling studies of quark-gluon plasma at energies over 100 GeV per nucleon.The paper discusses the radiation pressure dominated regime of relativistic ion acceleration, where ultra-intense electromagnetic waves interact with solid materials, transforming wave energy into the energy of ions. This regime, known as the "laser piston" (LP) regime, is highly efficient and can generate high-density ultra-short relativistic ion beams. The authors present a detailed analysis and three-dimensional particle-in-cell (PIC) simulations to support their findings. The LP regime involves two stages: (1) relativistic electron acceleration and charge separation, leading to relativistic ion energies, and (2) the accelerated foil acting as a plasma mirror, where the laser pulse is reflected, and the radiation pressure accelerates the ions further. The simulations show that the maximum ion energy can reach 30 GeV, with an efficiency of 30% for all ions. The authors suggest that this regime could be used in a laser-driven heavy ion collider, potentially enabling studies of quark-gluon plasma at energies over 100 GeV per nucleon.