• N L Singh

      Articles written in Pramana – Journal of Physics

    • α-Particle induced reactions on rhodium

      M S Gadkari N L Singh

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      Excitation functions for103Rh (α,xn);x = 1–4 and103Rh (α,αxn);x = 1–3 reactions were measured up to 50 MeV bombarding energy using stacked foil activation technique and high purity germanium (HPGe) γ-ray spectroscopy method. The experimental results were compared with calculations considering equilibrium as well as pre-equilibrium hybrid model of Blann (ALICE/90). It is found that the initial exciton configurationn0 = 4(4p0h) gives fairly good agreements for (α,xn) reactions. There seems to be indication of direct inelastic scattering effects in (α,αxn)-type of reactions.

    • Measurement of peak fluence of neutron beams using Bi-fission detectors

      R K Jain Ashok Kumar N L Singh L Tommasino B K Singh

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      Fission fragments and other charged particles leave tracks of permanent damage in most of the insulating solids. Damage track detectors are useful for personal dosimeters and for flux/dose determination of high-energy particles from accelerators or cosmic rays. A detector that has its principal response at nucleon energy above 50 MeV is provided by the fission of Bi-209. Neutrons produce the largest percentage of hadron dose in most high-energy radiation fields. In these fields, the neutron spectrum is typically formed by low-energy neutrons (evaporation spectrum) and high-energy neutrons (knock-on spectrum). We used Bi-fission detectors to measure neutron peak fluence and compared the result with the calculated value of neutron peak fluence. For the exposure to 100 MeV we have used the iThemba Facility in South Africa.

    • Influence of argon plasma treatment on polyethersulphone surface

      N L Singh S M Pelagade R S Rane S Mukherjee U P Deshpande V Ganeshan T Shripathi

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      Polyethersulphone (PES) was modified to improve the hydrophilicity of its surface, which in turn helps in improving its adhesive property. The modified PES surface was characterized by contact angle measurement, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Vicker’s microhardness measurement. The contact angles of the modified PES reduces from $49^{\circ}$ to $10^{\circ}$ for water. The surface free energy (SFE) calculated from measured contact angles increases from 66.3 to 79.5 mJ/m2 with the increase in plasma treatment time. The increase in SFE after plasma treatment is attributed to the functionalization of the polymer surface with hydrophilic groups. The XPS analysis shows that the ratio of O/C increases from 0.177 to 0.277 for modified PES polymer. AFM shows that the average surface roughness increases from 6.9 nm to 23.7 nm due to the increase in plasma treatment time. The microhardness of the film also increases with plasma treatment.

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