• Ramakrishna Gowda

      Articles written in Pramana – Journal of Physics

    • Photon interaction cross-sections and anomalous scattering factors of Cu and Ag

      Sandiago T K Umesh Ramakrishna Gowda

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      Total attenuation cross sections of copper and silver have been measured in the energy range 5 to 85 keV in a narrow beam good geometry set up using X- andγ-rays emitted from radio isotopes, by employing a high resolution hyper pure germanium detector. From the measured values, the photoeffect cross-sections have been derived by subtracting a small contribution of the sum of the theoretical coherent and incoherent scattering cross sections. The photoeffect cross-sections so obtained are found to be in better agreement with the unrenormalized values of Scofield [10]. These photoeffect cross-sections have been used to evaluate the dispersion corrections (also called anomalous scattering factors)f+ andf″ for the forward Rayleigh scattering amplitude by a numerical evaluation of the dispersion integral that relates them at the energies at which the cross-sections have been measured. To thef+ values so obtained, the relativistic corrections proposed by different investigators are included separately and the valuesf′ so obtained are compared with the available data and discussed. Possible conclusions are drawn from the present study.

    • X-ray fluorescence in some rare earth and high Z elements excited by 661.6 keV γ-rays

      T Yashoda S Krishnaveni Shivalinge Gowda TK Umesh Ramakrishna Gowda

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      The K-shell X-ray fluorescence cross sections are determined experimentally for 10 elements such as Pb, Hg, Ir, W, Lu, Tm, Dy, Tb, Gd and Nd at excitation energy of 661.6 keV associated with γ-rays of 137Cs radioisotope. The technique employed involves the measurement of total intensity of fluorescent K X-rays that follow the photoeffect absorption of a known flux of γ-rays using a well type Nal(Tl) detector. The obtained results are compared with the available theoretical values and other measured values.

    • Photon mass attenuation coefficients, effective atomic numbers and electron densities of some thermoluminescent dosimetric compounds

      Shivalinge Gowda S Krishnaveni T Yashoda T K Umesh Ramakrishna Gowda

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      Photon mass attenuation coefficients of some thermoluminescent dosimetric (TLD) compounds, such as LiF, CaCO3, CaSO4, CaSO4.2H2O, SrSO4, CdSO4, BaSO4, C4H6BaO4 and 3CdSO4.8H2O were determined at 279.2, 320.07, 514.0, 661.6, 1115.5, 1173.2 and 1332.5 keV in a well-collimated narrow beam good geometry set-up using a high resolution, hyper pure germanium detector. The attenuation coefficient data were then used to compute the effective atomic number and the electron density of TLD compounds. The interpolation of total attenuation cross-sections of photons of energyE in elements of atomic numberZ was performed using the logarithmic regression analysis of the data measured by the authors and reported earlier. The best-fit coefficients so obtained in the photon energy range of 279.2 to 320.07 keV, 514.0 to 661.6 keV and 1115.5 to 1332.5 keV by a piece-wise interpolation method were then used to find the effective atomic number and electron density of the compounds. These values are found to be in agreement with other available published values.

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