Browsing by Author "J.J. Das"

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A modular focal plane detector system for the heavy ion reaction analyzer at NSC, New Delhi
(Elsevier, 1996) D.O. Kataria; J.J. Das; N. Madhavan; P. Sugathan; A.K. Sinha; G. Dayanand; M.C. Radhakrishna; A.M. Vinodkumar; K.M. Varier; Mahendrajit Singh; N.V.S.V. Prasad
A detector system has been developed for the focal plane of the HIRA. It consists of two independent detectors, a low-pressure multiwire proportional counter (LP-MWPC) followed by a split-anode ionization detector. Details of the design and test results are presented. Using slow preamplifiers, the position resolution is ≥1 mm and the time resolution is estimated to be 1.5 ns for the LP-MWPC. The ionization detector gives 2.4% energy resolution for 150 MeV 28Si scattered off a gold target and the ΔZ/Z obtained for 28Si+27Al is 1/42 for Z=14. Some results for fusion and transfer studies for the 48Ti+58Ni and 28Si+68Zn systems, respectively, at energies around the Coulomb barrier, are presented to highlight the performance of the detector system.
Erratum: Loss of collectivity in 79Rb (European Physical Journal A (2006) 28 (277-281) DOI:10.1140/epja/i2005-10286-8)
(2006) R.K. Sinha; A. Dhal; P. Agarwal; S. Kumar; Monika; B.B. Singh; R. Kumar; P. Bringel; A. Neusser; R. Kumar; K.S. Golda; R.P. Singh; S. Muralithar; N. Madhavan; J.J. Das; K.S. Thind; A.K. Sinha; I.M. Govil; R.K. Bhowmik; J.B. Gupta; P.K. Joshi; A.K. Jain; S.C. Pancholi; L. Chaturvedi
[No abstract available]
High spin states in 70Ge
(2000) B. Mukherjee; S. Muralithar; G. Mukherjee; R.P. Singh; R. Kumar; J.J. Das; P. Sugathan; N. Madhavan; P.V. Madhusudanan Rao; A.K. Sinha; A.K. Pande; L. Chaturvedi; S.C. Pancholi; R.K. Bhowmik
High spin states in 70Ge nucleus have been studied in two different experiments using heavy ion fusion evaporation reaction. The Gamma Detector Array, comprising of eight Compton-suppressed High Purity Ge detectors, was used in conjunction with a recoil mass spectrometer - the HIRA - in order to identify and measure the transitions of this weakly populated nucleus. The level scheme is extended up to an excitation energy of 13 MeV for spin-parity 21- with several newly observed transitions placed in it. A rotational like band is also observed in this nucleus for the first time.
Indian National Gamma Array at Inter University Accelerator Centre, New Delhi
(2010) S. Muralithar; K. Rani; R. Kumar; R.P. Singh; J.J. Das; J. Gehlot; K.S. Golda; A. Jhingan; N. Madhavan; S. Nath; P. Sugathan; T. Varughese; M. Archunan; P. Barua; A. Gupta; M. Jain; A. Kothari; B.P.A. Kumar; A.J. Malyadri; U.G. Naik; Raj Kumar; Rajesh Kumar; J. Zacharias; S. Rao; S.K. Saini; S.K. Suman; M. Kumar; E.T. Subramaniam; S. Venkataramanan; A. Dhal; G. Jnaneswari; D. Negi; M.K. Raju; T. Trivedi; R.K. Bhowmik
A 4π multi-detector gamma-ray spectrometer named the Indian National Gamma Array (INGA) has been set up at the Inter University Accelerator Centre, New Delhi, for nuclear structure studies. The array is designed to incorporate twenty four Compton-suppressed Clover germanium detectors with a total photopeak efficiency ∼5%. The spectrometer along with sub-systems developed in-house like, mechanical support structure, high voltage power supplies, automatic liquid nitrogen filling system, front-end electronics and data acquisition system are described. The mechanical support structure facilitates the use of the Clover Germanium array with a recoil mass separator. The array has been used in a number of nuclear spectroscopic investigations. The in-beam and off-beam performance of the array are reported. © 2010 Elsevier B.V.
Indian National Gamma Array at IUAC
(Institute of Physics Publishing, 2011) S. Muralithar; K. Rani; R.P. Singh; R. Kumar; J.J. Das; J. Gehlot; K.S. Golda; A. Jhingan; N. Madhavan; S. Nath; P. Sugathan; T. Varughese; M. Archunan; P. Barua; A. Gupta; M. Jain; A. Kothari; B.P.A. Kumar; A.J. Malyadri; U.G. Naik; Raj Kumar; Rajesh Kumar; J. Zacharias; S. Rao; S.K. Saini; S.K. Suman; M. Kumar; E.T. Subramaniam; S. Venkataramanan; A. Dhal; G. Jnaneswari; D. Negi; M.K. Raju; T. Trivedi; R.K. Bhowmik
Indian National Gamma Array (INGA) is a 4π multi-detector gamma-ray spectrometer based on twenty four Compton-suppressed Clover Germanium detectors with a total photo peak efficiency ∼ 5 %. INGA was designed to perform high resolution gamma-ray spectroscopy to study nuclear structure at high spins with stable ion beams at Inter University Accelerator Centre (IUAC). Description of the facility and performance of the array are presented in this paper. Since its commissioning, a number of nuclear spectroscopic investigations have been carried out using the array.
Loss of collectivity in 79Rb
(Springer New York, 2006) R.K. Sinha; A. Dhal; P. Agarwal; S. Kumar; Monika; B.B. Singh; R. Kumar; P. Bringel; A. Neusser; R. Kumar; K.S. Golda; R.P. Singh; S. Muralithar; N. Madhavan; J.J. Das; K.S. Thind; A.K. Sinha; I.M. Govil; R.K. Bhowmik; J.B. Gupta; P.K. Joshi; A.K. Jain; S.C. Pancholi; L. Chaturvedi
High-spin states in 79Rb were populated in the reaction 63Cu(19F, p2n) 79Rb at E(beam) = 60 MeV. The lifetimes of the excited states of the πg9/2 positive-parity yrast band and of the πp3/2 negative-parity band in 79Rb were measured by the Doppler Shift Attenuation Method. The deduced transition quadrupole moments Qt are found to have a decreasing trend with rotational frequency for both the bands, consistent with those found experimentally in neighbouring nuclei.
Measurement of the transverse kinetic energies of argon recoil ions produced in 120 MeV Si8+-Ar collisions
(Springer New York, 1998) M.J. Singh; S.K. Goel; R. Shanker; D.O. Kataria; N. Madhavan; P. Sugathan; J.J. Das; D.K. Avasthi; A.K. Sinha
Measurements were carried out to deduce the transverse kinetic energies of highly charged argon recoil ions produced in single collisions of 120 MeV Si8+ ions with argon atoms in which the post collision charge states of the projectiles were not determined. A time of flight spectrometer was designed and fabricated to detect the charge states of recoils. Experimental procedures for optimizing the spectrometer for extraction, transmission and detection of recoils are described. A simple approach for determining the transverse kinetic energy of the recoil ions from FWHM of the peaks is reported. This method is shown to be independent of the choice of collision partners and requires only the knowledge of the physical values of "optimized parameters" of time-of-flight spectrometer used in the experiment. The transverse kinetic energy of the recoil ions determined from the present approach is found to vary from 0.03 eV for Ar+ to 4.02 eV for Ar10+. These values are compared with the results reported by earlier workers and are shown to follow a g2-behaviour up to a charge state q = 8+ of the recoil ions. © EDP Sciences Springer-Verlag 1998.
SCORPION: A system for coincidences between recoil and projectile ions at NSC, New Delhi
(Indian Academy of Sciences, 1997) M.J. Singh; S.K. Goel; R. Shanker; D.O. Kataria; N. Madhavan; P. Sugathan; J.J. Das; D.K. Avasthi; A.K. Sinha
An on-line facility to measure coincidences between the recoil ions and the scattered projectiles (SCORPION) has been designed, fabricated and commissioned at Nuclear Science Centre (NSC), New Delhi. The facility consists of a four jaw slit assembly, a time of flight (TOF) spectrometer, a parallel plate electrostatic charge analyser and a one dimensional position sensitive parallel plate avalanche counter (PPAC). Details of the design and working principles of various components and the test results obtained for the Siq+-Ar collision system are presented to highlight the performance of the system. A multiple loss of up to four electrons has been observed for 60 MeV Si4+ ions colliding with argon atoms in a single collision condition. Spectra of recoil ions detected in coincidence with a particular charge state of the scattered projectile show a bell shaped distribution as a function of the recoil charge state (r) for the electron loss events. However, the yield of recoil ions drops as r increases for the direct ionization channel. Also for electron loss, the peak of the recoil ion distribution is seen to shift to a higher recoil charge state as the number of lost electrons from the projectile increases.
Shape changes at high spin in 78Kr
(2006) A. Dhal; R.K. Sinha; P. Agarwal; S. Kumar; Monika; B.B. Singh; R. Kumar; P. Bringel; A. Neusser; R. Kumar; K.S. Golda; R.P. Singh; S. Muralithar; N. Madhavan; J.J. Das; A. Shukla; P.K. Raina; K.S. Thind; A.K. Sinha; I.M. Govil; P.K. Joshi; R.K. Bhowmik; A.K. Jain; S.C. Pancholi; L. Chaturvedi
High-spin states in 78Kr have been studied via the 63Cu (19F, 2p2n)78Kr reaction at a beam energy of 60 MeV using the Indian National Gamma Array (INGA). In this nucleus, lifetimes have been measured upto the I π=22+ level in the yrast positive-parity band and upto the I π=15- level in the negative-parity band using the Doppler Shift Attenuation Method (DSAM). The deduced transition quadrupole moments Qt's are found to decrease with rotational frequency for both the bands.
Shape coexistence and high spin states in Cr52
(2007) Rajesh Kumar; S.K. Chamoli; I.M. Govil; A. Dhal; R.K. Sinha; L. Chaturvedi; Z. Naik; C.R. Praharaj; S. Muralithar; R.P. Singh; N. Madhavan; P. Sugathan; J.J. Das; R.K. Bhowmik
High spin states in Cr52 have been populated by means of the reaction Al27(Si28,3p)Cr52 at a beam energy of 70 MeV and studied with an array, consisting of eight Compton-suppressed clover germanium detectors. Eleven new γ rays have been assigned to Cr52 and placed in the level scheme. The level structure of Cr52 has been extended up to Ex 10 MeV. Spins and parities have been assigned to many of the levels on the basis of directional correlations and linear polarization measurements. The band structures are discussed in the framework of cranked Woods-Saxon and deformed Hartree-Fock (HF) models. Both the oblate and prolate orbits are considered for J projection in the HF model. The K=0+ band is properly understood if we consider the J projection from both prolate and oblate orbits and collectivity shown by the K=4+ band to be accounted for by taking the J projection from prolate HF configurations. Thus there is prolate and oblate shape coexistence in Cr52. © 2007 The American Physical Society.
Shape evolution in odd-A 137 Pm
(Springer New York LLC, 2012) A. Dhal; R.K. Sinha; D. Negi; T. Trivedi; M.K. Raju; D. Choudhury; G. Mohanto; S. Kumar; J. Gehlot; R. Kumar; S. Nath; S.S. Ghugre; R.P. Singh; J.J. Das; S. Muralithar; N. Madhavan; J.B. Gupta; A.K. Sinha; A.K. Jain; I.M. Govil; R.K. Bhowmik; S.C. Pancholi; L. Chaturvedi
The odd mass nucleus 137Pm has been studied to high spins through the 109Ag(32S, 2p2n)137Pm reaction at an incident beam energy of 150 MeV. The de-exciting γ-rays were detected using an array of 18 Compton suppressed clover detectors. The level scheme of 137Pm has been extended up to Jπ = 43/2- and excitation energy of Ex ≅ 6 MeV with the observation of 42 new gamma transitions. The linear polarization (IPDCO) measurements for the γ-ray transitions have been done for the first time. The spin and parity assignments for most of the reported levels have been made using these results and the coincidence angular anisotropy (RDCO) measurements. The nuclear shape evolution is discussed in the light of Total Routhian Surface (TRS) and Cranked Shell Model (CSM) calculations. © 2012 SIF, Springer-Verlag Berlin Heidelberg.