Sugathan Pullanhiotan | Inter University Accelerator Centre (original) (raw)

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Papers by Sugathan Pullanhiotan

Chinese Physics C, Dec 2, 2022

Dissipative dynamics of nuclear fission is a well confirmed phenomenon described either by a Kram... more Dissipative dynamics of nuclear fission is a well confirmed phenomenon described either by a Kramers-modified statistical model or by a dynamical model employing the Langevin equation. Though dynamical models as well as statistical models incorporating fission delay are found to explain the measured fission observables in many studies, it nonetheless shows conflicting results for shell closed nuclei in the mass region 200. Analysis of recent data for neutron shell closed nuclei in excitation energy range 40−80 MeV failed to arrive at a satisfactory description of the data and attributed the mismatch to shell effects and/or entrance channel effects, without reaching a definite conclusion. In the present work we show that a well established stochastic dynamical code simultaneously reproduces the available data of pre-scission neutron multiplicities, fission and evaporation residue excitation functions for neutron shell closed nuclei 210 Po and 212 Rn and their isotopes 206 Po and 214,216 Rn without the need for including any extra shell or entrance channel effects. The calculations are performed by using a phenomenological universal friction form factor with no ad-hoc adjustment of model parameters. However, we note significant deviation, beyond experimental errors, in some cases of Fr isotopes.

EPJ Web of Conferences, 2017

Fission process is strongly influenced by entrance channel dynamical variables. Among these, the ... more Fission process is strongly influenced by entrance channel dynamical variables. Among these, the nuclear charge product, mass asymmetry and deformation play important role in fission dynamics. Reaction characteristics are distinguished by investigating the properties of fission mass and angular distributions. Experiments using actinide targets are challenging due to many conflicting results making unambiguous identification of quasi-fission difficult. At IUAC accelerator facility many experiments have been performed to make a systematic study of fission mechanism and role of entrance channel parameters and deformation. Fragment mass distribution, angular distribution and neutron multiplicity measurements are performed to study reactions using spherical and deformed targets.

Physics Letters B, 2016

Fission-fragment mass distributions were measured for 225,227 Pa nuclei formed in fusion reaction... more Fission-fragment mass distributions were measured for 225,227 Pa nuclei formed in fusion reactions of 19 F + 206,208 Pb around fusion barrier energies. Mass-angle correlations do not indicate any quasi-fission like events in this bombarding energy range. Mass distributions were fitted by Gaussian distribution and mass variance extracted. At below-barrier energies, the mass variance was found to increase with decrease in energy for both nuclei. Results from present work were compared with existing data for induced fission of 224,226 Th and 228 U around barrier energies. Enhancement in mass variance of 225,227 Pa nuclei at belowbarrier energies shows evidence for presence of asymmetric fission events mixed with symmetric fission events. This is in agreement with the results of mass distributions of nearby nuclei 224,226 Th and 228 U where two-mode fission process was observed. Two-mode feature of fission arises due to the shell effects changing the landscape of the potential-energy surfaces at low excitation energies. The excitation-energy dependence of the mass variance gives strong evidence for

Journal of Physics: Conference Series, 2016

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2015

ABSTRACT The characteristics and performance of a new detector system based on CsI(TI) scintillat... more ABSTRACT The characteristics and performance of a new detector system based on CsI(TI) scintillators, and its front-end electronics are presented. The detector system has been developed for the detection of light charged particles to investigate fusion–fission dynamics, and will also serve as ancillary detector for an array of neutron detectors. CsI scintillators are read by photo-diodes. The main feature of the array is its compact and simple high density front-end electronics which includes custom developed low noise charge sensitive preamplifiers (with very low power consumption for operation inside vacuum), NIM differential drivers, and commercially available Mesytec amplifiers with two different time constants for particle identification using a ballistic deficit technique.

Physical Review C

According to Stelson's neutron flow model the threshold barrier is correlated to the onset of neu... more According to Stelson's neutron flow model the threshold barrier is correlated to the onset of neutron flow. A systematic study of a large set of systems indicates that there exists a very good correlation between the threshold barrier and the intersurface distance after including the zero point motion of collective surface vibrations of the colliding nuclei in the prescription of Stelson. ͓S0556-2813͑96͒02908-1͔

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2008

The VAMOS spectrometer at GANIL is a large acceptance magnetic spectrometer employing a trajector... more The VAMOS spectrometer at GANIL is a large acceptance magnetic spectrometer employing a trajectory reconstruction technique to identify the reaction products. The spectrometer when coupled with the EXOGAM clover array provides a powerful tool for the spectroscopy of very weak reaction channels. Parameters are reconstructed using a numerical procedure with a polynomial relationship between the measured final coordinates and the quantities of interest. The coefficients of this polynomial function are determined from a numerical fit to the data generated from ray-tracing calculations using the ion optics code ZGOUBI. To reconstruct each parameter, a single polynomial is used with a set of coefficients that are valid across the full accepted phase space of the spectrometer. To further improve upon the reconstruction method, we developed an alternate procedure for reconstruction based on selecting an optimum set of trajectories and interpolating the data within these trajectories. For each detected event, a set of coordinates lying close to the measured trajectory are selected from the database and the target parameters of interest are determined by polynomial interpolation. The results for the reconstructed parameters using the two methods are presented.

Indian Journal of Physics

Indian Journal of Pure and Applied Physics

An in-flight radioactive ion beam (RIB) facility has been developed at Nuclear Science Centre (NS... more An in-flight radioactive ion beam (RIB) facility has been developed at Nuclear Science Centre (NSC), using the recoil mass spectrometer HIRA. The spectrometer separates the RIB species produced in the inverse reactions like (p.n), (d.n ), (3He,n) etc and transport them to the secondary target position. High purity 7Be of moderate intensity has been extracted with the set-up and used in experiment.

A joint project of INR, and Inter University Accelerator Centre (IUAC), New Delhi to study the cl... more A joint project of INR, and Inter University Accelerator Centre (IUAC), New Delhi to study the cluster structure of highly excited states of light nuclei is described. Proposed experiments will be carried out on the neutron beam INR, and ion beam 6Li in IUAC reactions 6Li +7Li →7Li +6Li * →7Li + t + τ, 6Li +7Li →7Be +6He * → 7Be + t + t, n + 7Li → 2H + 6He * → 2H + t + t. We present simulation results that demonstrate the possibility to obtain data on the structure of the levels in a wide range of excitation energies.

The European Physical Journal Conferences

Pramana, 1997

An on-line facility to measure coincidences between the recoil ions and the scattered projectiles... more 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).

EPJ Web of Conferences, 2011

... Rev. C 60, 044602 (1999). [6] TG Masterson, Nucl. Instrum. Methods 88, 61 (1970). [7] S. Venk... more ... Rev. C 60, 044602 (1999). [6] TG Masterson, Nucl. Instrum. Methods 88, 61 (1970). [7] S. Venkataramanan, Arti Gupta, KS Golda, Hardev Singh, Rakesh Kumar, RP Singh and RK Bhowmik, Nucl. Instr. and Meth. A 596, 248 (2008). ...

Nuclear Physics A, 2004

The angular distribution of 7 Be + 7 Li elastic scattering has been measured using 7 Be from the ... more The angular distribution of 7 Be + 7 Li elastic scattering has been measured using 7 Be from the Radioactive beam at Nuclear Science Centre, New Delhi at E cm = 9.87 MeV. A compact and highly efficient detector system in kinematic coincidence mode and an in-vacuum target transfer system have been developed to minimise contributions from unwanted channels. The angular ranges covered were θ cm = 42 o -66 o and θ cm = 114 o -138 o . The experimental angular distribution shows higher cross sections than the theoretical predictions at the backward angles. The experimental data could be fitted with an isospin dependent complex potential that is analogous to the Lane potential.