https://repository.auw.edu.bd/handle/123456789/735 2026-06-09T22:56:11Z https://repository.auw.edu.bd/handle/123456789/950 Neutron Capture Cross Section of Unstable 63Ni: Implications for Stellar Nucleosynthesis Meaze, AKM Moinul Haque The 63Niðn; Þ cross section has been measured for the first time at the neutron time-of-flight facility n_TOF at CERN from thermal neutron energies up to 200 keV. In total, capture kernels of 12 (new) resonances were determined. Maxwellian averaged cross sections were calculated for thermal energies from kT 1⁄4 5–100 keV with uncertainties around 20%. Stellar model calculations for a 25M star show that the new data have a significant effect on the s-process production of 63Cu, 64Ni, and 64Zn in massive stars, allowing stronger constraints on the Cu yields from explosive nucleosynthesis in the subsequent supernova. 2013-01-01T00:00:00Z https://repository.auw.edu.bd/handle/123456789/935 Angular distribution in the neutron-induced fission of actinides Meaze, AKM Moinul Haque Above 1 MeV of incident neutron energy the fission fragment angular distribution (FFAD) has generally a strong anisotropic behavior due to the combination of the incident orbital momentum and the intrinsic spin of the fissioning nucleus. This effect has to be taken into account for the efficiency estimation of devices used for fission cross section measurements. In addition it bears information on the spin deposition mechanism and on the structure of transitional states. We designed and constructed a detection device, based on Parallel Plate Avalanche Counters (PPAC), for measuring the fission fragment angular distributions of several isotopes, in particular 232Th. The measurement has been performed at n_TOF at CERN taking advantage of the very broad energy spectrum of the neutron beam. Fission events were recognized by back to back detection in coincidence in two position-sensitive detectors surrounding the targets. The detection efficiency, depending mostly on the stopping of fission fragments in backings and electrodes, has been computed with a Geant4 simulation and validated by the comparison to the measured case of 235U below 3 keV where the emission is isotropic. In the case of 232Th, the result is in good agreement with previous data below 10 MeV, with a good reproduction of the structures associated to vibrational states and the opening of second chance fission. In the 14 MeV region our data are much more accurate than previous ones which are broadly scattered. 2013-01-01T00:00:00Z https://repository.auw.edu.bd/handle/123456789/934 High-accuracy determination of the neutron flux in the new experimental area n TOF-EAR2 at CERN Meaze, AKM Moinul Haque A new high flux experimental area has recently become operational at the n TOF facility at CERN. This new measuring station, n TOF-EAR2, is placed at the end of a vertical beam line at a distance of approximately 20 m from the spallation target. The characterization of the neutron beam, in terms of flux, spatial profile and resolution function, is of crucial importance for the feasibility study and data analysis of all measurements to be performed in the new area. In this paper, the measurement of the neutron flux, performed with different solid-state and gaseous detection systems, and using three neutron- converting reactions considered standard in different energy regions is reported. The results of the various measurements have been combined, yielding an evaluated neutron energy distribution in a wide energy range, from 2 meV to 100 MeV, with an accuracy ranging from 2%, at low energy, to 6% in the high-energy region. In addition, an absolute normalization of the n TOF-EAR2 neutron flux has been obtained by means of an activation measurement performed with 197Au foils in the beam. 2013-01-01T00:00:00Z https://repository.auw.edu.bd/handle/123456789/933 Neutron research at the N_TOF facility (CERN): Results and perspectives Meaze, AKM Moinul Haque In the first ten years of operation, the neutron time-of-flight facility n_TOF at CERN has produced a large body of new and accurate data on neutron capture and fission cross sections, relevant to Nuclear Astrophysics and advanced nuclear technologies. In the next phase, with the construction of a second experimental area with a shorted flight path, the focus of the Collaboration will partially shift from high-resolution measurements of stable or long-lived isotopes, to high-flux measurements of isotopes of relatively short half-life, very low-cross sections, or available in very small quantities. The main results obtained so far at n_TOF and the future perspectives are here presented. 2013-01-01T00:00:00Z