Browsing by Author "N. Saneesh"

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Asymmetric fission around lead: The case of Po 198
(American Physical Society, 2019) Shilpi Gupta; C. Schmitt; K. Mahata; A. Shrivastava; P. Sugathan; A. Jhingan; K.S. Golda; N. Saneesh; M. Kumar; G. Kaur; L. Stuttgé; D. Arora; H. Arora; A. Chatterjee; K. Chauhan; S.K. Duggi; D.P. Kaur; V. Mishra; Prashant N. Patil; K. Rani
Asymmetric low-energy fission of neutron-deficient nuclei around lead is addressed with the measurement of fragment mass and total kinetic energy properties for the fissioning system Po198 produced in heavy-ion fusion. Interpretation of the measurement for such a transitional nucleus at finite excitation energy is challenging. The presence of asymmetric partitions is suggested by the observed weak dependence of the total kinetic energy on mass and by the nonmonotonic evolution of the fragment-mass distribution width with excitation energy. The interpretation is supported by microscopic model calculations as well as by the results of an advanced semiempirical code. Combined with previous experiments in the region, the present measurement contributes to establish the evolution of the fragment-mass distribution as a function of the fissioning system. The connection between the "new" and the "old" islands of asymmetric fission is discussed. © 2019 American Physical Society.
Fission dynamics and entrance-channel study in the Po 210 compound nucleus via light-particle multiplicities
(American Physical Society, 2023) Chetan Sharma; B.R. Behera; Shruti; Amit; Bharti Rohila; Amninderjeet Kaur; Subodh; Neha Dhanda; Ashok Kumar; P. Sugathan; A. Jhingan; K.S. Golda; N. Saneesh; Mohit Kumar; H. Arora; Divya Arora; H.P. Sharma
Neutron multiplicities, folding angle distribution, mass distribution, and mass-energy distribution are measured for the compound nucleus Po210 populated through the C12+Pt198 reaction at an excitation energy of 61.6 MeV. The measured neutron multiplicities are compared with the statistical model code joanne2 to extract total fission time for the Po210 compound nucleus. The total fission time (τtot) obtained for this system is (10±5)×10-21 s at 49 MeV and increases to (23±5)×10-21 at 61.8 MeV excitation energy indicating that dissipation increases with excitation energy. A comparison with τtot of the O18+Os192 reaction populating the same compound nucleus indicates the influence of entrance channel mass asymmetry on the fission time. Dynamical model calculations have been performed to understand the fusion dynamics for these reactions and it is observed that the formation time of the compound nucleus increases as we go from the asymmetric to the symmetric entrance channels. Also, these calculations predict that 93% of the total angular momentum lead to the formation of a fully equilibrated compound nucleus for the C12+Pt198 reaction whereas this percentage decreases to 84%, for the O18+Os192 reaction indicating a higher percentage of noncompound nuclear processes in the latter case. © 2023 American Physical Society.
Fission time scale from pre-scission neutron and α multiplicities in the O 16 + Pt 194 reaction
(American Physical Society, 2017) K. Kapoor; S. Verma; P. Sharma; R. Mahajan; N. Kaur; G. Kaur; B.R. Behera; K.P. Singh; A. Kumar; H. Singh; R. Dubey; N. Saneesh; A. Jhingan; P. Sugathan; G. Mohanto; B.K. Nayak; A. Saxena; H.P. Sharma; S.K. Chamoli; I. Mukul; V. Singh
Pre- and post-scission α-particle multiplicities have been measured for the reaction O16+Pt194 at 98.4 MeV forming Rn210 compound nucleus. α particles were measured at various angles in coincidence with the fission fragments. Moving source technique was used to extract the pre- and post-scission contributions to the particle multiplicity. Study of the fission mechanism using the different probes are helpful in understanding the detailed reaction dynamics. The neutron multiplicities for this reaction have been reported earlier. The multiplicities of neutrons and α particles were reproduced using standard statistical model code joanne2 by varying the transient (τtr) and saddle to scission (τssc) times. This code includes deformation dependent-particle transmission coefficients, binding energies and level densities. Fission time scales of the order of 50-65 ×10-21 s are required to reproduce the neutron and α-particle multiplicities. © 2017 American Physical Society.
Inference on fission timescale from neutron multiplicity measurement in 18O + 184W
(IOP Publishing Ltd, 2022) N.K. Rai; A. Gandhi; M T Senthil Kannan; S.K. Roy; N. Saneesh; M. Kumar; G. Kaur; D. Arora; K.S. Golda; A. Jhingan; P. Sugathan; T.K. Ghosh; Jhilam Sadhukhan; B.K. Nayak; Nabendu K Deb; Saumyajit Biswas; A. Chakraborty; A. Parihari; Ajay Kumar
The pre-scission and post-scission neutron multiplicities are measured for the 18O + 184W reaction in the excitation energy range of 67.23-76.37 MeV. Langevin dynamical calculations are performed to infer the energy dependence of fission decay time in compliance with the measured neutron multiplicities. Different models for nuclear dissipation are employed for this purpose. Fission process is usually expected to be faster at a higher beam energy. However, we found an enhancement in the average fission time as the incident beam energy increases. It happens because a higher excitation energy helps more neutrons to evaporate that eventually stabilizes the system against fission. The competition between fission and neutron evaporation delicately depends on the available excitation energy and it is explained here with the help of the partial fission yields contributed by the different isotopes of the primary compound nucleus. © 2022 IOP Publishing Ltd.
Measurement of neutron multiplicity to investigate the role of entrance channel parameters on the nuclear dissipation
(American Physical Society, 2019) N.K. Rai; A. Gandhi; Ajay Kumar; N. Saneesh; M. Kumar; G. Kaur; A. Parihari; D. Arora; K.S. Golda; A. Jhingan; P. Sugathan; T.K. Ghosh; Jhilam Sadhukhan; B.K. Nayak; Nabendu K. Deb; S. Biswas; A. Chakraborty
In the present work, the pre- and post-scission neutron multiplicities were measured for the reaction O18+W186 at different excitation energies populating the compound nucleus Pb204, using the National Array of Neutron Detectors (NAND) facility at IUAC, New Delhi, India. Here, we investigated the entrance channel effect on the nuclear dissipation involved in the heavy ion fusion-fission dynamics. The statistical model analysis was performed using the code vecstat. The prescribed reaction O18+W186 had similar value of the mass asymmetry as the system O16+Ta181 studied earlier, populating the compound nucleus Tl197. Specifically, we observed the similar behavior from both the systems against the nuclear dissipation, with the similar value of the mass asymmetry. The role of the entrance channel parameters on the nuclear dissipation was also discussed in the present work. © 2019 American Physical Society.
Newexperimental insights about dissipation near shell closure
(American Physical Society, 2025) Punit Dubey; Mahima Upadhyay; Mahesh Choudhary; Namrata Singh; Shweta R. Singh; Ajay Vinod Kumar; N. Saneesh; Mohit Praveen Kumar; Rishabh Prajapati; K. S. Golda; Akhil Jhingan; Sugathan Pullanhiotan; Jhilam Sadhukhan; Raghav Aggarwal; Kiran
The pre- and postscission neutron multiplicities have been determined for the fission of the compound nucleus (CN) 206Rn, induced by the reaction 28Si+178Hf within the excitation energy interval of 61.0–90.0 MeV. We intentionally formed the CN 206Rn, which is below the shell closure CN, to examine the variation in N/Z with total neutron multiplicity, as data for other compound nuclei of 208,210,212,214,216Rn have already been published in the literature. The present experimental investigations between N/Z and total multiplicities validate the theoretical claims made by various calculations. Specifically, it was observed that the total neutron multiplicity decreases as the compound nucleus approaches the shell closure and subsequently increases as it moves away from the shell closure. Furthermore, we have observed that, below the neutron shell closure, the dissipation in compound nuclei escalates with rising excitation energy, remains stable at the shell closure CN, and thereafter diminishes with increasing excitation energy above the shell closure CN. © 2025 American Physical Society
Role of viscosity in fusion-fission dynamics via simultaneously measured neutron and α -particle multiplicities
(American Physical Society, 2019) K. Kapoor; N. Bansal; Chetan Sharma; S. Verma; K. Rani; R. Mahajan; B.R. Behera; K.P. Singh; A. Kumar; H. Singh; R. Dubey; N. Saneesh; M. Kumar; A. Yadav; A. Jhingan; P. Sugathan; B.K. Nayak; A. Saxena; H.P. Sharma; S.K. Chamoli
The multiplicities of α particles and neutrons have been measured simultaneously for the reaction O16+Pt196 forming Rn212 compound nucleus at excitation energies of 56 MeV, 61 MeV, and 68 MeV. Neutrons and α particles were detected at various angles in coincidence with the fission fragments. To extract the contribution of pre- and postmultiplicities using the total α-particle and neutron spectra, moving source formalism was implemented. In the case of α particle, near scission contribution has also been extracted. Study of the fission mechanism using light particle emissions are helpful in understanding the detailed fusion-fission reaction dynamics. The statistical model code joanne2, which includes deformation-dependent particle transmission coefficients, binding energies and level densities, has been used to reproduce the measured multiplicities of neutrons and α particles by varying the transient (τtr) and saddle to scission (τssc) times. It is found that the fission time scales of the order of 50-70×10-21 sec are required to reproduce the neutron and α-particles multiplicities simultaneously. The fission time scales are the measure of the nuclear viscosity, which is responsible for the dynamic hindrance of the fission process. © 2019 American Physical Society.
Study of nuclear fusion-fission dynamics in 16O+194Pt reaction
(American Institute of Physics Inc., 2017) K. Kapoor; S. Verma; P. Sharma; R. Mahajan; N. Kaur; G. Kaur; B.R. Behera; K.P. Singh; H. Singh; R. Dubey; N. Saneesh; A. Jhingan; P. Sugathan; G. Mohanto; B.K. Nayak; A. Saxena; H.P. Sharma; S.K. Chamoli; I. Mukul; A. Kumar
Pre- and post-scission α-particle multiplicities have been measured for the reaction 16O + 194Pt at 98.4 MeV forming compound nucleus 210Rn. The α-particle's yield has been measured in coincidence with the fission fragments at various angles. The moving source analysis was performed to extract the alpha particle multiplicity which yielded the contribution of pre- and post- scission components. The pre-scission α-particle multiplicity has been compared with JOANNE2 statistical model code predictions to extract fission time scale and which is observed to be around 55zs (1zs=10-21s). © 2017 Author(s).