K. M. Balakrishna

K fluorescence yield measurements in rare earth and heavy elements

K fluorescence yields were measured for 16 elements Cu, Mo, Ag, Cd, Sn, Pr, Sm, Gd, Dy, Ho, Yb, Ta, W, Pb, Th and U using a HPGe low energy photon detector employing the reflection geometry set-up. The target atoms were excited using 59.5 keV and 279.2 keV gamma rays from Am-241 and Hg-203 radioactive sources of strengths 20 mCi and 40 mCi respectively. An effective shielding arrangement was used to minimize the background and multiple scattering. Elemental foils of uniform aerial density and purity better than 99.9% were used as targets. The data were recorded in a 4K multichannel analyser. Among the K fluorescence yields measured in this work nine cases constitute the first measurement. The results are compared with the literature experimental values for available cases and also with the semiempirical fits and theoretical predictions.

Total K fluorescence yields for Fe, Cu, Zn, Ge and MO

Total K fluorescence yields were determined for five low Z elements Fe, Cu, Zn, Ge and Mo using reflection geometry and employing a Xe filled proportional counter having a 5 mil (1.27*10-2 cm) Be window. The targets were photoexcited using 59.5 keV soft gamma rays as primary radiation from an 241Am radioactive source of strength 300 mCi. An effective graded shielding arrangement was used to minimize the background radiation and multiple scattering. Elemental foils of uniform thickness and purity better than 99.5% were used as targets. The fluorescence spectra were recorded in a 1 k multichannel analyser. The data was carefully analysed and total K fluorescence yields were determined. The results obtained were 0.350, 0.425, 0.471, 0.538 and 0.758 for Fe, Cu, Zn, Ge and Mo respectively. The experimental results are compared with theoretical predictions, semiempirical estimates and also earlier results obtained by other methods.

Experimental effective atomic numbers for the photoelectric process in some alloys at 84 and 145 keV

The total attenuation coefficients are measured for seven alloys at 84 and 145 keV by the transmission method using a good geometry setup employing a NaI(Tl) scintillation spectrometer. The scattering contributions are deduced using the theoretical cross sections taken from the recent literature and are subtracted from the measured total cross sections to get the photoelectric cross sections. Finally, the effective atomic numbers are obtained from the graph of cross section versus the atomic number. Results are compared with semiempirical estimates and are found to be in good agreement. Results are also compared with the available experimental values, some of which are reported at 412 keV and some at 52.5 keV and a good agreement is noted.

Verification of incoherent scattering functions at intermediate photon momentum transfer

Experimental whole atom differential incoherent scattering cross sections were measured for Cu, Mo, Ag, Cd, Sn, Pr, Sm, Gd, Dy, Ho, Yb, Ta, W, Th and U for the 90 degrees scattering of 145.4 and 84.3 keV gamma rays. The scattering experiments were conducted in a reflection geometry set up with a graded shielding arrangement. A 133 cm3 HpGe detector was used to detect the scattered gamma rays. The cross sections were measured using Al as standard. From the measured cross sections the incoherent scattering functions were extracted. The results are compared with theory and with the experimental values reported in literature for available cases. The electron binding effects and the validity of the incoherent scattering functions at intermediate momentum transfer are discussed.

Experimental study on coherent scattering of 145.4 and 279.2 keV gamma rays by medium and heavy elements

Differential cross sections for coherent scattering of 145.4 and 279.2 keV gamma rays were measured for Cu, Mo, Ag, Cd, Sn, Pr, Sm, Gd, Dy, Ho, Yb, Ta, W, Pb, Th and U employing a reflection geometry set-up with a graded shielding arrangement. A 133 cm3 HPGe detector was used to detect the scattered gamma rays. The measured cross sections were compared with the experimental values in literature and with the numerically calculated results using S-matrix theory for available cases. From the measured cross sections the form factors corresponding to 8.295 and 15.923 AA-1 photon momentum transfer were extracted. The results are discussed in the light of the predictions of form factor formalisms.

Caesium-137 concentration in Kaiga environment

Measurement of radioactivity levels in various environmental matrices at the Kaiga nuclear power plant and the surrounding environs has been carried out on a routine basis to establish the baseline background radiation level prevailing in the region. Measurement of the concentration of Cs-137 in environmental matrices is necessary to estimate the amount of fallout of this radionuclide in the region and to assess the long term impact of the nuclear power plant on the environment.