Experimental control of laser proton acceleration beyond 50 MeV

We report on the ongoing plasma accelerator development at the HZDR, moving from plasma-acceleration studies towards real plasma-accelerators that can be controlled and applied in the lab.
We show experimental investigations of proton acceleration from laser-irradiated solid foils with the DRACO PW laser, where highest proton cut-off energies were achieved for temporal pulse shape parameters well different from that of a Fourier transform limited (FTL) pulse. Controlled spectral phase modulation of the driver laser by means of an acousto-optic programmable dispersive filter enabled us to manipulate the temporal laser pulse shape and to study the effect on proton acceleration from thin foil targets. The results show that short and asymmetric pulses generated by positive third order dispersion values are favourable for proton acceleration and can lead to maximum energies of 60 MeV for thin plastic foils. Assuming appropriate control of the spectral phase of the laser and comparable temporal contrast conditions, we believe that the presented method can be universally applied to improve the proton acceleration performance using any other laser system operated in the PW regime.