Observation of energetic deuteron ions accelerated from the rear surface of laser-irradiated flat-foil targets

Summary form only given. Deuteron ions accelerated from the rear-surface of laser-irradiated flat-foil targets have been observed with energies up to 7 MeV. The observations were made using a compact-design Thomson Parabola Spectrometer with a static magnetic field strength of around 0.8 T and an electric field strength of around 3 kV. The ions were accelerated from the rear surface by the Target-Normal-Sheath-Acceleration mechanism. The targets were 500×500×3 μm³ silicon substrates, etched from rigid wafers, coated with 50 nm of Al. The laser was incident into the etched-out cavity at the front of the wafer. The rear surface of the wafer was coated with a solution of deuterated plastic (Cambridge isotopes CD 98%) dissolved in toluene in the ratio of 1:150. Upon evaporation of the toluene, a residue of CD with a thickness of about 1 μm constituted the deuteron source and the target final layer. The experiments were performed on the GHOST laser facility at the University of Texas at Austin. The laser, which is focused to a radius of around 6 μm, provided up to 2 J of energy in a pulse of duration 115 fs corresponding to a mean intensity exceeding 10¹⁹ Wcm^-2.