  We experimentally demonstrate a notably enhanced acceleration of protons to
high energy by relatively modest ultrashort laser pulses and structured
dynamical plasma targets. Realized by special deposition of snow targets on
sapphire substrates and using carefully planned pre-pulses, high proton yield
emitted in a narrow solid angle with energy above 21MeV were detected from a
5TW laser. Our simulations predict that using the proposed scheme protons can
be accelerated to energies above 150MeV by 100TW laser systems.
