Browsing by Author "J.Rama Rao"

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Absolute yields of some fission products in the fast neutron induced fission of 238U
(1987) S. Ram; N.L. Singh; S.K. Bose; J.Rama Rao
Fission-track registration characteristics of Lexan plastic track detector immersed in aqueous solution of uranyl nitrate have been studied. An attempt has been made to measure absolute fission yields of some fission products in the 14 MeV induced fission of 238U using track etch-cum-gamma ray spectrometry. Yields of 10 fission-products with half life ranging up to several hours and mass numbers in the region 99-157 are reported. © 1987.
Excitation functions for radioactive isotopes produced by alpha particle induced reactions with silver
(1987) N.L. Singh; S. Agarwal; L. Chaturvedi; J.Rama Rao
Stacked foil activation technique and Ge(Li) γ-ray spectroscopy have been used for the determination of the excitation functions, up to 50 MeV, of seven reactions, 107Ag(α, n), (α, 2n), (α, αn), (α, α2n); 109Ag(α, 2n), (α, 3n) and (α, 4n). Since, natural as the target has two odd-mass stable isotopes of about equal abundance, 107Ag(51.83%) and 109Ag(48.17%), their activation in some cases gives the same residual nucleus through different reaction channels, but with very different Q-values. In such cases, the individual reaction cross sections are separated with the help of the ratio of the theoretical cross sections. The theoretical predictions based on a pre-equilibrium exciton model, with an initial exciton configuration of n0 = 5 (5p0h), appear to give a good fit to the experimental data. © 1987.
Excitation functions of alpha particle induced reactions in cobalt in the energy range 10-120 MeV using variable energy cyclotrons
(1987) J.Rama Rao; A.V.Mohan Rao; S. Mukherjee; R. Upadhyay; N.L. Singh; S. Agarwal; L. Chaturvedi; P.P. Singh
Alpha particle induced reactions on the target element cobalt were investigated from 10 to 120 MeV, using foil stack activation technique and the Ge(Li) gamma ray spectroscopy method. Ten excitation functions for reaction residues 51Cr, 52,54Mn, 56,57Ni, 59Fe and 56,57,58,60Co were measured, of which 59Co(α, p6n)56Ni reaction was measured for the first time. A comparison with pre-equilibrium hybrid model was made using initial exciton number, n0 = 4 (4pOh). It is observed that for (α, xnypzα) type reactions the agreement is within a factor of 2, while for (α, xnyp) type the disagreement is generally by more than an order of magnitude. © 1987.
Investigation of alpha particle induced reactions on thulium
(Springer India, 1992) A.V. Mohan Rao; S. Mukherjee; J.Rama Rao
Alpha particle induced reactions on the target element thulium were investigated up to 75 MeV, using foil-stack activation technique and Ge(Li) gamma ray spectroscopy method. Excitation functions for eight reactions of the type169Tm(α, xn), x=1 - 4;169Tm(α, pxn), x=3; and169Tm(α, αxn), x=1, 2, 4 were investigated. Of these, four reactions169Tm(α, p3 n),169Tm(α, αn),169Tm(α, α2 n)169Tm(α, α4 n), were studied for the first time and in the remaining four reactions, some 19 new energy-point cross-sections were measured for the first time. The experimental cross-sections were compared with the predictions of pre-equilibrium hybrid model, as well as the more recent index model, using the initial excition number, n 0=4 (4 p0 h). Both the models show better agreement in respect of (α, xnyp) type of reactions. However they are equally bad for (α, αxn) type of reactions which involve the α-particle in the exit channels, and for which some direct reaction contributions are indicated. © 1993 Indian Academy of Sciences.
Pre-equilibrium analysis of the excitation functions of (α, xn) reactions on silver and holmium
(Società Italiana di Fisica, 1991) S. Mukhrjee; A.V. Mohan Rao; J.Rama Rao
The excitation functions of the109Ag (α, 2n),107Ag(α,2n),109Ag(α,4n),165Ho (α, xn);x=1, ..., 4 reactions were studied upto 75 MeV, using the stacked foil activation technique and Ge(Li) gamma-ray spectroscopy method. Of these, four reactions were studied for the first time using high-resolution Ge(Li)/HPGe detector, and some twenty-three new energy point cross-sections were measured for the first time. A comparison with pre-equilibrium, hybrid model (ALICE/85/300) and the more recent index model was made using the initial exciton number n o=4 (4p 0h), and a general agreement was found in all the reactions. © 1991 Società Italiana di Fisica.
Simulation technique for the measurement of fast neutron reaction cross sections
(1986) J.Rama Rao; N.L. Singh; S. Singhal; A.V.Mohan Rao; S. Mukherjee; L. Chaturvedi
There is a need for precision measurement of the fast neutron cross sections, wherever they are, a few tens of millibarns or less in magnitude. In these cases, since large samples and large solid angles have to be used to get good statistics, complex corrections have to be applied for self-scattering and self-absorption effects in the target and pile-up effects in the detector. We have measured fast neutron cross sections for 58Ni(n, 2n)57Ni, 75As(n, α)72Ga, 138Ba(n, p)138Cs and 138Ba(n, α)135m, gXe reactions usi powder technique together with a high resolution (1.78 keV fwhm for 1.33 MeV photons) HPGe detector. Special care is taken to determine the above corrections experimentally by a "simulation technique", which enables the exact magnitude of corrections to be known precisely. © 1986.