• B K Godwal

      Articles written in Pramana – Journal of Physics

    • Saha’s ionization equation for highZ elements

      B K Godwal S K Sikka

      More Details Abstract Fulltext PDF

      Saha’s ionization equation has been solved for highZ elements with the aim of providing input for opacity calculations. Results are presented for two elements, tungsten and uranium. The ionization potentials have been evaluated using the simple Bohr’s formula with suitable effective charges for ions. The reliability of the free electron density, ion concentrations, etc., obtained from the Saha’s equation solutions has been checked by comparing thePT andET computed from them with those given by the Thomas-Fermi-Dirac equation of state. The agreement between the two is good from temperatures above 0.2 keV.

    • Opacities of high temperature highZ plasmas

      B K Godwal S K Sikka

      More Details Abstract Fulltext PDF

      A procedure is described for computation of opacities for highZ plasmas. Bound-bound, bound-free, free-free and scattering processes are considered. The inputs for these have been obtained by solving IEEOS form of Saha’s equation. Detailed calculations of opacities have been done for tungsten and uranium up to 10 keV of temperature.

    • Volume variation of nuclear Grüneisen parameter for equation of state studies

      B K Godwal

      More Details Abstract Fulltext PDF

      The method of first principle pseudopotential is used to simulate the volume variation of nuclear Grüneisen parameter. The elements Al and Be, for which Neal’s experimental data exist are investigated. The nuclear Grüneisen obtained from the details of phonon frequencies are in better agreement with the experimental data as compared to those obtained from approximate Slater and Dugdale-MacDonald methods, often used in shock wave studies.

    • Shock Hugoniot calculations and melting in Pb

      B K Godwal S K Sikka R Chidambaram

      More Details Abstract Fulltext PDF

      Shock Hugoniot calculations are carried out for lead (Pb) using both solid and liquid state theories. The Hugoniots in solid and liquid cases are in mutual agreement within the experimental uncertainties. However, the shock temperatures are quite different as computed from solid and liquid state theories. This fact can perhaps be used to detect melting along the shock Hugoniot provided the shock temperatures are accurately measured.

    • On the nature of the dhcp to fcc transition under pressure in Pr and Pr-Th alloys

      V Vijayakumar B K Godwal S K Sikka R Chidambaram

      More Details Abstract Fulltext PDF

      The results of electrical resistance (R), thermoelectric power (TEP) and X-ray diffraction measurements on praseodymium (Pr) and its alloys with thorium under pressure are reported. The maximum inR vsP curve exhibited by Pr persists only in the dhcp phase of PrTh alloy. X-ray measurements confirmed that in the alloys also the maximum inR vsP curve is due to the dhcp → fcc transition. Thus the behaviour of Pr and Pr-Th alloys is different from that of La and its alloys with Ce and Th where the maximum in theR vsP curve is electronic in origin and is exhibited by the dhcp, fcc and dist fcc phases.

    • Electronic structure of MgB2

      P Modak R S Rao B K Godwal S K Sikka

      More Details Abstract Fulltext PDF

      Results of ab initio electronic structure calculations on the compound MgB2 using the FPLAPW method employing GGA for the exchange-correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, c/a ratio and the bulk modulus, all of which are in excellent agreement with experiment. We obtain the mass enhancement parameter by using our calculated D (EF) and the experimental specific heat data. The Tc is found to be 24.7 K.

    • Effects of non-local thermodynamic equilibrium conditions on numerical simulations of inertial confinement fusion plasmas

      N K Gupta B K Godwal

      More Details Abstract Fulltext PDF

      Effects of non-local thermodynamic equilibrium (non-LTE) condition on emission and hydrodynamics of typical inertial confinement fusion (ICF) plasmas are studied. The average degree of ionization at high temperatures is seen to be much lower compared to the values obtained from Thomas-Fermi scaling or Saha equation for high-Z element like gold. LTE and non-LTE predictions for emitted radiation from laser-driven gold foil are compared with the experimental results and it is seen that non-LTE simulations show a marked improvement over LTE results. The effects of one group and multigroup, LTE and non-LTE approximations of radiation transport on hydrodynamic parameters are studied for laser-driven aluminium and gold foils. It is further seen that non-LTE and multigroup effects play an important role in predicting conversion efficiency of laser light to X-rays.

  • Pramana – Journal of Physics | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.