Ultra-high quality, ultra-high current proton beams produced with a laser-virtual cathode sheath accelerator

By structuring the rear surface of a foil, modulations in the transverse phase space are produced, which resemble fiducial "beamlets" within the envelope of the expanding plasma. This allows for mapping the expansion of the beam envelope during the latter, sheath expansion phase. Using this technique that allows to directly image the initial accelerating sheath, transverse phase space for protons of different energy is fully reconstructed. For protons of up to 10 MeV, the transverse emittance is as low as 0.002 mm mrad, i.e. 100-fold better than typical RF accelerators and at a substantially higher ion current (kA range)