• S K Singh

      Articles written in Pramana – Journal of Physics

    • Nuclear effects in the structure functions

      E Marco E Oset S K Singh

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      By using a relativistic framework and accurate nuclear spectral function the structure functions F2A andF3A of deep inelastic charged lepton and neutrino scattering are calculated in nuclei and results are presented.

    • Weak pion production from nuclei

      S K Singh M Sajjad Athar Shakeb Ahmad

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      The charged current pion production induced by neutrinos in12C,16O and56Fe nuclei has been studied. The calculations have been done for the coherent as well as the incoherent processes assuming Δ dominance and takes into account the effect of Pauli blocking, Fermi motion and the renormalization of Δ in the nuclear medium. The pion absorption effects have also been taken into account

    • Effect of upflowing field-aligned electron beams on the electron cyclotron waves in the auroral magnetosphere

      Sushil Kumar S K Singh A K Gwal

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      The role of low density upflowing field-aligned electron beams (FEBs) on the growth rate of the electron cyclotron waves at the frequencies $\omega_{r}$ < $\Omega_{­e}$, propagating downward in the direction of the Earth's magnetic field, has been analysed in the auroral region at $\omega_{e}/\Omega_{e}$ < 1 where $\omega_{e}$ is the plasma frequency and $\Omega_{­e}$ is the gyrofrequency. The FEBs with low to high energy ($E_{b}$) but with low temperature ($T_{|b}$) have no effect on these waves. The FEBs with $E_{b}$ < 1 keV and $T_{|b}$ (> 1.5 keV) have been found to have significant effect on the growth rate. Analysis has revealed that it is mainly the $T_{|b}$ which inhibits the growth rate (magnitude) and the range of frequency (bandwidth) of the instability mainly in the higher frequency spectrum. The inhibition in the growth rate and bandwidth increases with increase in $T_{|b}$. The FEBs with less $E_{b}$ (giving drift velocity) reduce growth rate more than the beams with larger $E_{b}$. The inhibition of growth rate increases with the increase in the ratio $\omega_{e}/\Omega_{e}$ indicating that the beams are more effective at higher altitudes.

    • Measurement of high-power microwave pulse under intense electromagnetic noise

      Amitava Roy S K Singh R Menon D Senthil Kumar R Venkateswaran M R Kulkarni P C Saroj K V Nagesh K C Mittal D P Chakravarthy

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      KALI-1000 pulse power system has been used to generate single pulse nanosecond duration high-power microwaves (HPM) from a virtual cathode oscillator (VIRCATOR) device. HPM power measurements were carried out using a transmitting–receiving system in the presence of intense high frequency (a few MHz) electromagnetic noise. Initially, the diode detector output signal could not be recorded due to the high noise level persisting in the ambiance. It was found that the HPM pulse can be successfully detected using wide band antenna, RF cable and diode detector set-up in the presence of significant electromagnetic noise. Estimated microwave peak power was $\sim 59.8$ dBm ($\sim 1$ kW) at 7 m distance from the VIRCATOR window. Peak amplitude of the HPM signal varies on shot-to-shot basis. Duration of the HPM pulse (FWHM) also varies from 52 ns to 94 ns for different shots.

    • The effect of nonlinearity in relativistic nucleon–nucleon potential

      B B Sahu S K Singh M Bhuyan S K Patra

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      A simple form for nucleon–nucleon (NN) potential is introduced as an alternative to the popular M3Y form using the relativistic mean field theory (RMFT) with the non-linear terms in 𝜎 -meson for the first time. In contrast to theM3Y form, the new interaction becomes exactly zero at a finite distance and the expressions are analogous with the M3Y terms. Further, its applicability is examined by the study of proton and cluster radioactivity by folding it with the RMFT-densities of the cluster and daughter nuclei to obtain the optical potential in the region of proton-rich nuclides just above the double magic core 100Sn. The results obtained were found comparable with the widely used M3Y $NN$ interactions.

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