Active manipulation of the spatial energy distribution of laser-accelerated proton beams

In English The spatial energy distributions of beams of protons accelerated by ultrahigh intensity (>10^19 W/cm2) picosecond laser pulse interactions with thin foil targets are investigated. Using separate, low intensity (<10^13 W/cm2) nanosecond laser pulses, focused onto the front surface of the target foil prior to the arrival of
the high intensity pulse, it is demonstrated that the proton beam profile can be actively manipulated. In
particular, results obtained with an annular intensity distribution at the focus of the low intensity beam are
presented, showing smooth proton beams with a sharp circular boundary at all energies, which represents a
significant improvement in the beam quality compared to irradiation with the picosecond beam alone.