Browsing by Author "N.L. Singh"

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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.
Alpha-induced reactions on gold
(1988) N.L. Singh; A.V. Mohan Rao; S. Mukherjee; R. Upadhyay; R.K. Jain; S.K. Bose; L. Chaturvedi; J. Rama Rao
The excitation functions of the 197Au(( alpha ,n), ( alpha ,2n), ( alpha ,3n), (d,2pn), ( alpha , alpha n) and ( alpha , alpha 3n)) reactions were measured up to 75 MeV. The experimental data were compared with the calculated values obtained by means of a hybrid model (ALICE/85/300) using the initial exciton number n0=4(4p0h) and the level density parameters a=A/8. A general agreement was found for all except the ( alpha , alpha n) and ( alpha , alpha 3n) reactions, where the disagreement was by about two orders of magnitude.
Analysis of the excitation functions from alpha particle induced reactions up to 120 MeV
(Royal Swedish Academy of Sciences, 1997) S. Mukherjee; N.L. Singh; A.V. Mohan Rao; L. Chaturvedi; P.P. Singh
Alpha particle induced reactions in the target element niobium were investigated in the energy range 30 to 120MeV. Thirteen excitation functions were measured for the production of 96Tc, 95m+gTc, 95Nb, 92mNb, 90Nb, 88Zr, 88Zr, 88Zr, 88Y, 87m+gY and 88Y. Secondly a comparison with a pre-equilibrium index model has been made using the initial exciton number n0 = 4 (4p0h) and level density parameter a = A/8. In general the shapes of the excitation functions were fairly well reproduced with the model predictions. However, the agreement between theoretical and experimental excitation functions for the (a, zzxnyp) type of reactions is only within a factor of 5.
Comparative Study of Pre-Equilibrium Models and Mechanism of Alpha Particle Induced Reactions
(1990) N.L. Singh; S. Agarwal; J. Rama Rao
Excitation functions of (α, xn yp zα) reactions on 93Nb and 169Tm have been measured upto 50 MeV by stacked-foil activation technique with a view to improve the quality of data in the case of 169Tm, which was earlier measured with a poor resolution scintillation detector. Comparisons are presented with the predictions of three pre-equilibrium models (i.e. Exciton, Hybrid and Index Models). While for {α, xn) type of reactions reasonably explainable pre-compound contributions are found, there seem to be indications of direct inelastic scattering effects in (α, αxn) type of reactions in medium and heavy nuclei. © 1990, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.
Evaluation of the nuclear excitation functions of fast neutron-induced reactions on 52Cr and 56Fe isotopes
(Scientific Publishers, 2019) A. Gandhi; N.K. Rai; P.K. Prajapati; B.K. Nayak; A. Saxena; B.J. Roy; N.L. Singh; S. Mukherjee; Yu N Kopatch; I.N. Ruskov; D.N. Grozdanov; N.A. Fedorov; A. Kumar
In this article, we present the nuclear excitation functions of the fast neutron-induced reactions 52Cr(n,p)52V, 52Cr(n,α)49Ti, 52Cr(n,2n)51Cr, 56Fe(n,p)56Mn, 56Fe(n,α)53Cr, and 56Fe(n,2n)55Fe, because these measurements are critical to estimate the level of the neutron activation for the fusion reactor structural materials. The theoretical computer codes TALYS-1.8 and EMPIRE-3.2.2 have been used for the calculation of the excitation functions. The theoretical calculations consider different nuclear reaction models, level density models and optical model potentials. The calculated excitation function results are compared with the existing experimental data obtained from the IAEA-EXFOR database, as well as with those available in the TENDL-2017 and ENDF/B-VIII.0-evaluated nuclear data libraries. The obtained results show the variation in excitation functions for different level density models. Moreover, we have studied the contribution from different reaction mechanisms in total reaction cross-section which varies with the incident neutron energy. These excitation function results can be useful to estimate the important parameters of nuclear reactors, such as nuclear heating, nuclear transmutation rates, and waste management etc. This kind of information can enhance the basic understanding of the mechanism of the fast neutron-induced nuclear reactions. © 2019, Indian Association for the Cultivation of Science.
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.
Experimental study of the transfer-induced fission fragment angular distribution in the Li 6 + U 238 reaction
(American Physical Society, 2017) A. Parihari; G. Mohanto; Gurpreet Kaur; A. Jhingan; K. Mahata; R.G. Thomas; P.C. Rout; E.T. Mirgule; V.V. Desai; B. Srinivasan; C. Joshi; V. Mishra; M. Kushwaha; Shilpi Gupta; D. Sarkar; S.V. Suryanarayana; A. Shrivastava; N.L. Singh; A. Misra; B.K. Nayak; A. Saxena
Transfer-induced fission fragment angular distribution measurements have been carried out in Li6+U238 reaction at beam energies of 36 and 40 MeV in coincidence with projectile-like fragments. The fission fragment anisotropies for α- and deuteron-transfer-induced fission reactions are obtained with respect to the recoil direction. The anisotropy values for transfer-induced fissions are observed to be either similar or lower than the inclusive measurement. In order to quantitatively understand the present experimental data on transfer-induced fission, anisotropy values have been compared with the preequilibrium fission model considering ground-state spin of the projectile and/or target. It is found that the model predicts the inclusive and exclusive anisotropy data reasonably well. © 2017 American Physical Society.
Franck-Condon factors and r-centroids for the triplet band system of CO molecule
(1961) N.L. Singh; D.C. Jain
It has been verified that the Morse potential function is a good approximation for the representation of the potential energy curves of d 3π and a3π electronic states of the CO molecule. The Franck-Condon factors for the triplet band system have been computed by the direct method of numerical integration of the Morse wave functions. The r-centroids for this band system have been calculated by (i) the direct method of numerical integration and (ii) the quadratic equation method of Nicholls and Jarmain. A close agreement is obtained between the values of r-centroids evaluated by both the methods. Assuming that the electronic transition moment is approximately constant, the relative population of the vibrational levels of the d3π state of the CO molecule has been calculated using Herman and Rakotoarijimy's experimental data on the relative intensity measurement of the triplet bands developed in the presence of xenon.
Infra-red absorption spectrum of ortho-fluorotoluene
(1967) G. Joshi; N.L. Singh
Infra-red absorption spectrum of o-fluorotoluene has been recorded in the range 2-15 μ on a Perkin-Elmer spectrophotometer (Model 13U) with NaCl optics. Frequencies observed have been proposed to different modes of vibration, assuming Cs symmetry for the molecule. © 1967.
Infra-red spectrum of o-bromotoluene
(1966) G. Joshi; N.L. Singh
The infra-red spectrum of o-bromotoluene has been investigated in liquid phase in the region 700-4590 cm-1. Assignments of the observed frequencies have been proposed by assuming Cs symmetry for the molecule. © 1966.
Mathematical analysis of isobaric decay chain in alpha particle induced reactions
(Springer India, 1993) S. Mukherjee; N.L. Singh; J. Rama Rao
A detailed mathematical formalism is developed from the first principles, to separate out the fractional contributions of the cross-section σ g and σ p for the production of the two isobaric precursor nuclei- grand parent and parent, respectively, to the cross-section σ d for the formulation of the residual nucleus of interest. The analytical work of separating out such contributions gives a meaningful picture to the comparison with the theoretical predictions of hybrid model, using the initial excition number n 0 = 4(4 p0 h). © 1993 the Indian Academy of Sciences.
Measurement and analysis of isomeric cross section ratios in the reaction Nb93(α,2n)Tc95: Pre-equilibrium reaction mechanism
(American Physical Society, 2005) S. Mukherjee; N.L. Singh; G. Kiran Kumar; L. Chaturvedi
Isomeric cross-section ratio and excitation functions have been measured for Nb93(α,2n)Tc95m+g reactions up to 120 MeV. The ratio and the excitation functions were interpreted in terms of the theoretical results obtained by two models COMPLET and STAPRE, which include preequilibrium effects. The experimental results were fairly well reproduced by the COMPLET calculations, which take into account the angular momentum removal in preequilibrium emission in an approximate way. Conversely, STAPRE calculations show a better agreement for isomeric ratio, but the experimental excitation function is underestimated by almost a factor of 2. © 2005 The American Physical Society.
Measurement of 90Zr(n,2n)89Zr and 90Zr(n,p)90mY reaction cross-sections in the neutron energy range of 10.95 to 20.02 MeV
(Springer Science and Business Media B.V., 2021) Mayur Mehta; N.L. Singh; R.K. Singh; Siddharth Parashari; P.V. Subhash; H. Naik; R.D. Chauhan; R. Makwana; S.V. Suryanarayana; S. Mukherjee; A. Gandhi; J. Varmuza; K. Katovsky
The (n,2n) and (n,p) reaction cross-sections of 90Zr isotope have been measured in 10.95 to 20.02 MeV neutron energy range by using activation and off-line γ-ray spectrometric technique. 27Al(n,α)24Na and 115In(n,n’)115mIn monitor reactions have been used to measure the neutron fluence. The reaction cross-sections were estimated from TALYS-1.9 and EMPIRE-3.2.2 codes by making the selection of different input parameters. The uncertainties in the measurement were estimated using covariance analysis. The present results have been compared with the data measured previously by different authors and available in different evaluated nuclear data files. © 2021, Akadémiai Kiadó, Budapest, Hungary.
Measurement of peak fluence of neutron beams using Bi-fission detectors
(2012) R.K. Jain; Ashok Kumar; N.L. Singh; L. Tommasino; B.K. Singh
Fission fragments and other charged particles leave tracks of permanent damage in most of the insulating solids. Damage track detectors are useful for personal dosimeters and for flux/dose determination of high-energy particles from accelerators or cosmic rays. A detector that has its principal response at nucleon energy above 50 MeV is provided by the fission of Bi-209. Neutrons produce the largest percentage of hadron dose in most high-energy radiation fields. In these fields, the neutron spectrum is typically formed by low-energy neutrons (evaporation spectrum) and high-energy neutrons (knock-on spectrum). We used Bi-fission detectors to measure neutron peak fluence and compared the result with the calculated value of neutron peak fluence. For the exposure to 100 MeV we have used the iThemba Facility in South Africa. © Indian Academy of Sciences.
Measurement of Th 232 (n,γ) reaction cross sections in the neutron energy range of 11-19 MeV
(American Physical Society, 2018) Siddharth Parashari; S. Mukherjee; A.P. Singh; Vibha Vansola; H. Naik; B.K. Nayak; Rajnikant Makwana; S.V. Suryanarayana; N.L. Singh; Mayur Mehta; Y.S. Sheela; M. Karkera; R.D. Chauhan; S.C. Sharma
The cross sections for the Th232(n,γ) reaction have been measured in the neutron energy range of 11-19 MeV by using activation and offline γ-ray spectrometric techniques. The neutrons of desired energy were obtained by the Li7(p,n) reaction using a proton beam of 13-21 MeV from the 14UD BARC-TIFR Pelletron facility at Mumbai, India. The Th232(n,γ) reaction cross sections were calculated using the computer code talys-1.8. The uncertainties in the measurement have been studied using covariance analysis of the experimental data. The results from the present work have been compared with the evaluated data of ENDF/B-VII.1 and JENDL-4.0 as well as the theoretically calculated values based on talys-1.8, and were found to be in good agreement. The outcome of the present work is important for the development of future fast reactors and accelerator driven subcritical systems (ADSs). © 2018 American Physical Society.
Non-equilibrium effects in alpha-particle-induced reactions in light, medium and heavy nuclei up to 120 mev
(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 elements vanadium, niobium and holmium were investigated in the energy range from 10 to 120 MeV, using the foil stack activation technique and Ge(Li) gamma-ray spectroscopy. The excitation functions of six reactions of the (alpha, xn) type were studied, of which three reactions 51V(alpha, n)54Mn, 165Ho(alpha ,2n)167Tm and 165Ho(alpha ,4n)165Tm were measured for the first time in the energy range from 80 to 120 MeV. A preliminary theoretical comparison with the pre-equilibrium hybrid model was made using an initial exciton number of n0=4 (4p0h) and general agreement was found for all except the 51V(alpha , n) and 93Nb(alpha , n) reactions at high energies. © 1987 IOP Publishing Ltd.
Recovery of the electrical insulation of a van de Graaff accelerator's charging belt by vacuum drying
(1985) V. Shrinet; N.L. Singh; S.K. Agrawal; G.P. Mishra; A.K. Nigam
The insulation of a moisture exposed “leaky” charging belt of AN-400 Van-de-Graaff Accelerator was successfully restored by vacuum drying. Although the drying time is of nearly one week, the technique is comparatively easy, risk free and superior to other alternative techniques and does not require dismantling of the belt. Copyright © 1986 by The Institute of Electrical and Electronics Engineers, Inc.
Relative intensities in the triplet system of CO bands
(1961) N.L. Singh; D.C. Jain
[No abstract available]
Rotational structure of the 2650-2850 Angstrom system of the BiF molecule
(1968) B.S. Mohanty; D.K. Rai; K.N. Upadhya; N.L. Singh
The rotational structure of the (0, 0) and (0, 1) bands of the 2650-2850 Angstrom system of the BiF molecule has been photographed in emission in the third order of a 35 ft concave grating spectrograph (dispersion, 0.22 Angstrom mm-1) and their rotational analysis carried out. The nature of the upper and lower states of this system has been discussed.