Description
Sponsored by School of Physics, University of the Witwatersrand
Cosmic rays are comprised largely of high energy protons and alpha particles which create large amounts of secondary particles through spallation when they interact with our atmosphere. At aviation altitudes the radiation field is made up predominantly of neutrons in the energy range 1 - 100 MeV [1]. During space weather events, such as solar flares, the number of energetic particles entering...
Neutron-based nuclear techniques such as fast neutron analysis (FNA) and thermal neutron analysis (TNA) are among the most powerful techniques for elemental analysis in small and bulk samples [1, 2]. The techniques are rapid, non-destructive, and are capable of multi-elemental analysis of samples with complex matrices. Neutron-based techniques are often used in the minerals industry, where...
The goal of this work is to research photon interaction parameters of four meteorite samples which have various elemental contents from the scientific literature. Mass attenuation coefficients, effective atomic number values, effective electron density values, coherent scattering cross sections, incoherent scattering cross sections, photoelectric absorption cross sections, pair production...
The use of Energy Density Functional (EDF) method within a relativistic framework showed, this last decades, that it can both describe the bulk properties of nuclei (radii, GS energy, binding energy, ...)[1] as well as clusters formation[2].
The study of cluster structures allow for many applications ranging from $\alpha$ or cluster decay to many different kinds of excitations.
This last few...
The level structure of neutron rich nucleus, $^{78}$As has been investigated at the low- and medium-spin regime through the alpha-induced fusion evaporation reaction, at varying beam energies, using the mylar backed enriched $^{76}$Ge target. The de-excited gamma rays were detected using the INGA (Indian National Gamma Array) spectrometer stationed at VECC, Kolkata, India. The level scheme of...
In this work, we modify the Davydov-Chaban Hamiltonian describing the collective motion of a $\gamma$-rigid atomic nucleus by allowing the mass to depend on nuclear deformation. Exact analytical expressions are derived for energy spectra as well as normalized wave functions for Kratzer potential. The model called Z(4)-DDMD (Deformation Dependent Mass with Kratzer potential), is achieved by...
PEPT Cape Town has pioneered the development of Gallium-68 based tracer particle analogues for use in positron emission particle tracking studies of granular and multiphase systems. The accuracy of the measured data relies strongly on how representative the tracer particle analogue is to the media of interest in these dynamic systems. The ability to control and manipulate the tracer...
Direct neutron capture measurements on short-lived radionuclides can be extremely challenging, if not impossible using current techniques. Therefore, indirect methods have been developed. A new apparatus was installed at the Los Alamos Neutron Science Center (LANSCE) to measure neutron total cross sections on small radioactive samples as an indirect means to tightly constrain their...
Particle-hole symmetry reveal some degenerate experimental observable for nuclei having equal N$_{p}$N$_{n}$. Up to date, E(2$^+$), E$_{4^+}$/E$_{2^+}$, B(E2; $2^+ \rightarrow 0^+$), spectroscopic factors for alpha decay, binding energy and moment of inertia have been investigated as a function of N$_{p}$N$_{n}$[1]. Recently, it has been shown that nuclei having particle-hole symmetry reveal...
Evidence for fusion hindrance in $^{12}$C + $^{24}$Mg was suggested by a recent experiment where the excitation function was over-estimated by standard CC calculations, and a pronounced indication of an S factor maximum vs energy was observed [1].
This system is slightly heavier than those of astrophysical interest, like $^{12}$C + $^{12}$C and $^{16}$O + $^{16}$O. Further measurements on...
The proton and neutron Fermi levels in nuclei with mass number A ~ 50 - 60 lie around the N = Z = 28 magic number. This shell gap is comparatively smaller which might have made the doubly magic $^{56}$Ni (N = Z = 28) a soft core [1]. The 1g$_{9/2}$ orbital, lies above fp orbital, has shape driving effect which leads to deformation and collectivity. Therefore, in these nuclei there is a...
A prompt and delayed $\gamma$-ray spectroscopy of neutron-deficient isotope $^{187}$Pb has been performed using the recoil-decay tagging and the isomer-decay tagging techniques at Argonne Gas-Filled Analyzer (AGFA). A new 4.66(4) $\mu$s isomer and a strongly-coupled band on top of it were identified. The band looks nearly identical to a band built on top of the 7/2$^{-}$[514] Nilsson orbital...
The formal concept of isospin has been introduced to explain the apparent exchange symmetry between neutrons and protons. However, if the nuclear force were the same for protons and neutrons properties such as masses and excitation energies would depend only on the mass number A. Recent studies have shown that the Coulomb force cannot account for all deviations, suggesting that other...
Keywords: LaBr3(Ce) detector; Background radiation; Gamma radiation; Detection limits
Abstract
NaI(Tl) detectors have for long been the preferred scintillation detector for radioisotope identification. However, one of the most profound shortcomings of this detector is its poor spectral resolution. A suitable replacement for NaI(Tl) is the LaBr3(Ce) detector. This detector shows...
B. P. Monteiro, K. C. C. Pires, R. Lichtenthäler, O. C. B. Santos
Departamento de Física Nuclear, Instituto de Física, Universidade de São
Paulo, 05508-090, SP, Brasil
A study of the mechanisms involved in the production of alpha particles from
reactions induced by a 6He radioactive beam on a 9Be light target, is presented. The
experimental data was obtained using the RIBRAS...
Electromagnetic excitations in finite nuclei represent one of the most important probes of relevance in nuclear structure and dynamic. Various aspects of magnetic dipole (M1) mode have been considered due to their relevance for nuclear properties associated e.g., to unnatural-parity states and spin-orbit splittings. Specifically, M1 spin-flip excitations are analog of Gamow-Teller (GT)...
The isotope $^{212}$Po has two-protons and neutrons outside the doubly-magic nucleus $^{208}$Pb and it may be assumed that the nuclear structure can be well described within the standard shell-model. But various experimental properties, such as the short-lived ground state are inconsistent with this model and better predicted by an $\alpha$-clustering model. The B(E2) values of the decays of...
The nuclear matrix elements of neutrinoless double-beta decay for nuclei 76Ge, 82Se, 100Mo, 130Te, and 150Nd are studied within the triaxial projected shell model, which incorporates simultaneously the triaxial deformation and quasiparticle configuration mixing. The low-lying spectra, the B(E2: 0+ to 2+) values, and the occupancies of single-particle orbits are reproduced well. The effects of...
Geant4 is a Monte Carlo based simulation toolkit utilized for the geometry and tracking of particles transport through matter. Geant4 offers variety of geometrical constructions, visualization, and multi-threading features, which are hard to find in simulating codes such as MCNP, FLUKA and FISPACTII. Evaluation of neutron radiation damage by means of Primary Knock-out Atoms (PKAs) and...
Recent studies of nuclear reactions involving weakly bound stable nuclei, $^{6,7}$Li and $^{9}$Be have revealed several interesting phenomena [1]. The low breakup threshold, small binding energy, and cluster structure are some of the unique features of these nuclei, which strongly influence the reaction dynamics at near barrier energies. The simultaneous measurement of complete/ incomplete...
HPGe detectors are one of the most important components of experimental nuclear physics. Therefore, a deeper understanding of them is required for better utilization of the available resources. Simulations allow us to do that in a faster way while also pointing to unaccounted processes in case of a mismatch between simulated and measured spectra. While there exist many simulation routines to...
Fusion-evaporation reactions have been proven very successful in populating excited states of deformed nuclei. The rare-earth region has been the focus of various studies (using Coulex etc) aiming at the understanding of nuclear structure and providing information on the details of the reaction mechanism. The Gd isotopes belong to this group of nuclei and despite the available spectroscopic...
The microscopic structure of the low-energy electric dipole response, commonly denoted as the Pygmy Dipole Resonance (PDR), was studied for $^{120}$Sn in a $^{119}$Sn$(d,p\gamma)^{120}$Sn experiment, using the SONIC@HORUS setup at the University of Cologne. Unprecedented access to the single-particle structure of excited $1^-$ states below and around the neutron-separation threshold was...
One of the current limitations of predicting the nuclear astrophysics r-process abundance is the lack of data on neutron-rich isotopes; measured neutron-capture cross-sections are the scarcest data. These cross-sections are also invaluable for nuclear reactions and structure in general. The current limitations come from the instability of the target and the projectiles. We proposed a method...
Abstract
Barrier distribution is a very sensitive tool for understanding fusion process in the presence of various possible channel couplings. There exist two experimental methods for investigating barrier distributions: (i) by the measurement of fusion excitation function and (ii) by the measurement of quasi-elastic excitation function. Among the two methods of measurements, the...
