• S Sharma

      Articles written in Pramana – Journal of Physics

    • Effect of lateral energy transport on ablation pressure scaling in laser irradiated planar foil targets

      L J Dhareshwar P A Naik S Sharma H C Pant

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      Experimental investigations on ablatively accelerated thin plastic foil targets irradiated by a 6J, 5 nsec Nd: glass laser pulse, were conducted using shadowgraphy technique. A 2 nsec, 0.53 µm probe pulse, derived from the main laser was used for recording the foil motion. It was observed that 6 µm plastic foils could be accelerated to a velocity of about 3 × 106 cm/sec for an incident laser intensity of 5 × 1013 W/cm2 and the corresponding ablation pressure was 0.4 Mbar. Ablation pressure (P) scaling against absorbed laser intensity (Ia) was slower (PIa0.4) for a smaller laser focal spot (30 µm) as compared to the scaling (PIa0.7) for a larger focal spot (500 µm). This result has been explained considering the loss due to lateral energy transport from the laser plasma interaction region.

    • Calorimetric study of laser-irradiated thin foil targets

      T S Shirsat S Sharma H C Pant

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      Hydrodynmaic efficiency of laser-irradiated thin aluminum and gold-coated aluminum targets was experimentally determined using a specially designed cone calorimeter. Velocity of the accelerated target and ablation pressure were also estimated from the experimental data. The laser irradiance range used in the experiments was between 1012 and 1013 watts/cm2. Experiments indicate that the fall in the hydrodynamic efficiency due to gold coating on aluminum target is about 12% at an irradiance of 8 × 1012 W/cm2.

    • Dielectric properties of Pb(Mg1/4Zn1/4Nb1/2)O11/4

      S Sharma R N P Choudhary R Sati

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      Polycrystalline samples of Pb(Mg1/4Zn1/4Nb1/2)O11/4 have been synthesized by high temperature columbite precursor solid state reaction technique. Using X-ray diffraction (XRD) technique, compound formation in single phase cubic structure was observed and XRD analysis provided preliminary structural data. Detailed studies of dielectric properties of the compound reveal that this compound has high dielectric constant and diffuse phase transition in a wide range of temperatures around the Curie temperature. The charge deficiency of the compound presumably gets compensated in the high temperature columbite precursor process of sample preparation which is supported by single phasic form of the material.

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