Articles written in Pramana – Journal of Physics

    • On the formation of amorphous layers by interdiffusion in zirconium-copper system

      K Bhanumurthy G K Dey S Banerjee S K Khera M K Asundi

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      Formation of amorphous phase by solid state reaction has been observed in bulk copper-zirconium couples. Transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and differential scanning calorimetry (DSC) techniques have been employed to detect and study the amorphous phase. The experimental observations have been explained with a model, which considers the breakdown of the a-zirconium lattice due to the solute enrichment beyond a certain limit where the nucleation of the amorphous phase becomes thermodynamically possible. The present-experiments convincingly show that amorphous phase can form in bulk diffusion couples made from large-grained well-annealed material and conclusively establish that the presence of crystal defects in high concentrations is not a pre-requisite for the formation of amorphous phase.

    • Consolidation of YBaCuO powders by shock loading

      N C Soni Ram Prasad Ashok Mohan M D Vora S Banerjee C V Tomy S K Malik H S Yadav K R K Rao

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      Superconducting oxide-copper monoliths have been fabricated by shock-wave loading using cylindrical and plane geometries. Bulk densities up to 96% T.D. have been obtained by varying detonation parameters. The superconducting properties, interface bonding and microstructure of the compacts have been evaluated.

    • Spherical shells of positive density - can they be of non-positive mass?

      A K RayChaudhuri S Banerjee

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      Spherical shells of fluid in general relativity are considered. The density is assumed to be spatially uniform and it is found that there may be three cases of positive, negative and vanishing Schwarzschild mass of the shell although the density and the pressure are both positive throughout. However the negative mass case has to be associated with a singularity representing a negative mass particle and so is unphysical. The zero mass solution has the intriguing feature that the geometry on either side of the shell is Minkowskian and the space is closed. This closure of the space saves the present result from being in contradiction with the positive energy theorems. Earlier investigations claiming zero-mass distributions are also discussed.

    • An automated thermal relaxation calorimeter for operation at low temperature (0.5 K<T<10 K)

      S Banerjee M W J Prins K P Rajeev A K Raychaudhuri

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      We describe an automated calorimeter for measurement of specific heat in the temperature range 10 K>T>0.5 K. It uses sample of moderate size (100–1000 mg), has a moderate precision and accuracy (2%–5%), is easy to operate and the measurements can be done quickly with He4 economy. The accuracy of this calorimeter was checked by measurement of specific heat of copper and that of aluminium near its superconducting transition temperature.

    • Quantum chromodynamics: Working group report

      Sourendu Gupta D Indumathi S Banerjee R Basu M Dittmar RV Gavai F Gelis D Ghosh Sourendu Gupta D Indumathi Asmita Mukherjee

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      This is the report of the QCD working group at WHEPP-6. Discussions and work on heavy ion collisions, polarized scattering, and collider phenomenology are reported.

    • Space-charge solitary waves and double layers in n-type compensated semiconductor quantum plasma


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      Using quantum hydrodynamic (QHD) model and standard reductive perturbation method, we have investigated the formation and characteristics of space-charge solitary waves and double layers in n-type compensated drifting semiconductor plasma with varying doping profiles. Through numerical analysis, it is shown that thestructures of space-charge solitary waves and double layers depend significantly on electron drift and compensation parameter which measures a comparative proportion of the donor, acceptor and intrinsic ion concentrations.

    • Investigation of non-uniform magnetic field on the beam particle energy exchange


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      This paper investigates the effect of a non-uniform magnetic field on beam particle energy exchange with three-dimensional particle-in-cell (3D-PIC) simulations. For this investigation, high current (kA range) planar sheet beam-driven rippled rectangular waveguide (RRWG) has been considered. For PIC simulations, beam current density was varied by changing the cathode cross-section (CS) in terms of thickness (beam thickness (BT)) with a common cathode width of 10 mm. There are four BTs (1 mm, 2 mm, 3 mm and 4 mm) and for each BT, seven types of magnetic field lines with the same magnitude of 0.6 T are used. These include one uniform magnetic field andsix non-uniform magnetic field patterns. In this paper, the complete structural design of RRWG to generate output power up to around 45 MegaWatt (MW) with a particular type of non-uniform magnetic field pattern/periodicity to guide the sheet electron beam-driven RRWG is discussed. The application of a non-uniform magnetic field pattern to a 2D sheet electron beam with spatial distribution or periodicity at minimum gaps (typically ≤ 1 mm) leads to the enhancement in output power at voltages operational in the backward region of the device.

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