Laser-driven acceleration of protons from hydrogenated annealed silicon targets

This paper provides the first demonstration that an hydrogenated annealed crystalline silicon may be used as a source of protons in laser-driven acceleration experiments. We analyze and compare the proton production from two silicon targets excited by a sub-nanosecond laser. One target (treated) was hydrogenated and annealed, while the other (untreated) did not undergo these procedures. The experimental results show that for the treated target, the number of generated protons is ∼1.4×10¹⁵ sr⁻¹ while for the other it is ∼3.6×10¹³ sr⁻¹. Their maximum energy is about 2 MeV with a laser intensity three order of magnitude lower than in previous experiments. We obtain an increase of 80% in the proton kinetic energy and of 200% in the proton current as well as a large amount of Si^q+ ions (1⩽q⩽14) with respect to the untreated target. A deconvolution procedure based on a Boltzmann-like distribution is applied for the analysis of time-of-flight (TOF) spectra of proton and silicon ion beams.