  A remarkable ion energy increase is demonstrated by several-stage
post-acceleration in a laser plasma interaction. Intense short-pulse laser
generates a strong current by high-energy electrons accelerated, when an
intense short-pulse laser illuminates a plasma target. The strong electric
current creates a strong magnetic field along the high-energy electron current
in plasma. During the increase phase of the magnetic field, the longitudinal
inductive electric field is induced for the forward ion acceleration by the
Faraday law. The inductive acceleration and the target-normal sheath
acceleration in the multi stages provide a unique controllability of the ion
energy. By the four-stage successive acceleration, our 2.5-dimensional
particle-in-cell simulations demonstrate a remarkable increase in ion energy by
a few hundreds of MeV; the maximum proton energy reaches 254MeV.
