Davinder Siwal

A new approach of denoising the regular and chaotic signals using Empirical Mode Decomposition: comparison and application.

The Empirical Mode Decomposition has been used to present a new approach for denoising of regular and chaotic time series originating from the nonlinear systems. The proposed filtering approach is based on the frequency distribution of different Intrinsic Mode Functions (IMFs). It provides complete frequency and noise strength information present in the data set. The actual frequencies in an experimental data set are distributed among different IMFs which are subsequently disentangled through the algorithm resulting into filtered as well as noise components. The filtered signal is produced only after a suppression (hard threshold) of noise components. The noise strength present in the data set is produced by the identified noisy IMFs. This innovative approach has been tested for linear, nonlinear, and chaotic types of calculated data sets with various levels of simulated noise strengths and results have been compared with the existing methods. The validity of the present approach is confirmed by experimentally observed astrophysical data as well as data from a neutron detector. A sharp improvement in the signal strength has been observed with the proposed method in comparison to the existing methods.

Effect of fissility in fission time scales for 16,18O+194,198Pt systems

The pre-scission neutron multiplicities have been studied for 16,18O+194,198Pt at 50, 61, 71.7, 79 MeV excitation energy populating 210,212,214,216Rn compound nuclei having fissility 0.735, 0.732, 0.729, 0.726 respectively. Fission Time scales were extracted from the measured pre-scission neutron multiplicity and statistical model PACE2. The effect of fissility on fission time scales has been measured. It is found that fission time scales increases in a consistent way with fissility of the compound nuclei (CN) populated. The fission delays extracted for different CN are in good agreement with earlier published data for heavier systems [1, 2]. In the present work it is shown systematically that the fission time scales generally increases with fissility value of CN.

Fusion and transfer reactions around the Coulomb barrier for 28Si+90,94Zr systems

Fusion excitation functions and transfer probabilities were measured for 28Si+90,94Zr systems around the Coulomb barrier, using the recoil mass separator, Heavy Ion Reaction Analyzer (HIRA) at Inter University Accelerator Centre (IUAC), New Delhi. The aim of these experiments was the study of coupling effects of inelastic and transfer channels on the sub-barrier fusion cross section enhancement. The experimental fusion cross sections were found to be strongly enhanced as compared to one dimensional barrier penetration model (1-d BPM) predictions in both the cases. The trend of data could be easily reproduced theoretically using coupled channels code CCFULL in the case of 28Si+90Zr but the observed enhancement could not be explained in the case of 28Si+94Zr, which may be attributed to the coupling of multinucleon transfer channels as both isotopes have similar collective strengths. The transfer probabilities in the case of 94Zr were found to be substantially higher than for 90Zr in the sub-barrier region.

Dipole bands in high spin states of 57135La78

High spin states of 135La have been investigated using the reaction 128Te(11B,4n)135La at a beam energy of 50.5 MeV. Two negative parity dipole bands (ΔI = 1) have been established. Crossover E2 transitions have been observed for the first time in one of the dipole bands. For the Tilted Axis Cranking (TAC) calculations, a three-quasiparticle (3qp) configuration π(h11/2)1⊗ν(h11/2)−2 and a five-quasiparticle (5qp) configuration π(h11/2)1(g7/2/d5/2)2⊗ν(h11/2)−2 have been taken for the two negative parity dipole bands. The comparison of experimental observables with TAC calculations supports the configuration assignments for both the dipole bands.

βdecay of102Y produced in projectile fission of238U

The population of 102Zr following the β decay of 102Y produced in the projectile fission of 238U at the GSI facility in Darmstadt, Germany has been studied. 102Y is known to s decay into 102Zr via two states, one of high spin and the other low spin. These states preferentially populate different levels in the 102Zr daughter. In this paper the intensities of transitions in 102Zr observed are compared with those from the decay of the low-spin level studied at the TRISTAN facility at Brookhaven National Laboratory and of the high-spin level studied at the JOSEF separator at the Kernforschungsanlage Julich.

β decay of 102Y produced in projectile fission of 238U

The population of 102Zr following the β decay of 102Y produced in the projectile fission of 238U at the GSI facility in Darmstadt, Germany has been studied. 102Y is known to s decay into 102Zr via two states, one of high spin and the other low spin. These states preferentially populate different levels in the 102Zr daughter. In this paper the intensities of transitions in 102Zr observed are compared with those from the decay of the low-spin level studied at the TRISTAN facility at Brookhaven National Laboratory and of the high-spin level studied at the JOSEF separator at the Kernforschungsanlage Julich.

Isomers in Neutron-rich Lead Isotopes Populated via the Fragmentation of 238U at 1 GeV A

Neutron-rich nuclei beyond N = 126 in the lead region were populated by fragmenting a 238U beam at 1 GeV A on a Be target and then separated by the Fragment Separator (FRS) at GSI. Their isomeric decays were observed, enabling study of the shell structure of neutron-rich nuclei around the Z=82 shell closure. Some preliminary results are reported in this paper.

Enhanced 0{sub g.s.}{sup +}->2{sub 1}{sup +} E2 transition strength in {sup 112}Sn

Two consecutive Coulomb excitation experiments were performed to excite the 2{sub 1}{sup +} states of {sup 112,116}Sn using a {sup 58}Ni beam. For {sup 112}Sn a B(E2arrow up) value of 0.242(8) e{sup 2} b{sup 2} has been determined relative to the known value of {sup 116}Sn. The present value is more precise than previous measurements and shows a clear discrepancy from the expected parabolic dependence between the doubly magic nuclei {sup 100}Sn and {sup 132}Sn. It implies that the reduced transition probabilities are not symmetric with respect to the midshell mass A=116.