Measurement and comparison of NaNO3 powder concealed in opaque and semi-transparent plastic bottles are carried out through conventional Raman spectroscopy and spatially offset Raman spectroscopy individually. The action mechanism why the spatially offset Raman spectroscopy can effectively detect the medium concealed in the non-transparent bottle is analyzed. The spatially offset Raman spectroscopy breaks through the detection neck of the conventional Raman spectroscopy (the detection depth is small and cannot detect the ingredient of the subsurface under non-transparent medium), and the measurement and identification of the substance concealed in the non-transparent medium (opaque/semi-transparent plastic) bottle have been realized.
Proton acceleration experiments were carried out by a 1.2×10 18 W/cm 2 ultra-short laser interaction with solid foil targets. The peak proton energy observed from an optimum target thickness of 7 µm in our experiments was 2.1 MeV. Peak proton energy and proton yield were investigated for different foil target thicknesses. It was shown that proton energy and conversion efficiency increased as the target became thinner, on one condition that the preplasma generated by the laser prepulse did not have enough shock energy and time to influence or destroy the target rear-surface. The existence of optimum foil thickness is due to the effect of the prepulse and hot electron transportation behavior on the foil target.
Forward fast protons are generated by the moderate-intensity laser-foil interaction. Protons with maximum energy 190 keV are measured by using magnetic spectrometer and CR-39 solid state track detectors along the direction normal to the rear surface. The experimental results are also modeled by the particle-in-cell method, investigating the timevarying electron temperature and the rear sheath field. The temporal and spatial structure of the sheath electrical field, revealed in the simulation, suggests that these protons are accelerated by target normal sheath acceleration (TNSA) mechanism.
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