  Laser-solid interaction can lead to the acceleration of protons to tens of
MeV. Here, we show that a strong enhancement of this acceleration can be
achieved by splitting the laser pulse to two parts of equal energy and opposite
incidence angles. Through the use of two- and three-dimensional
Particle-In-Cell simulations, we find that the multi-pulse interaction leads to
a standing wave pattern at the front side of the target, with an enhanced
electric field and a substantial modification of the hot electron generation
process. This in turn leads to significant improvement of the proton spectra,
with an almost doubling of the accelerated proton energy and five-fold
enhancement of the number of protons. The proposed scheme is robust with
respect to incidence angles for the laser pulses, providing flexibility to the
scheme, which should facilitate its experimental implementation.
