S. Ertürk

Discovery of 157 W and 161 Os

The nuclides 157W and 161Os have been discovered in reactions of 58Ni ion beams with a 106Cd target. The 161Os α-decay energy and half-life were 6890±12 keV and 640±60 μs. The daughter 157W nuclei β-decayed with a half-life of 275±40 ms, populating both low-lying α-decaying states in 157Ta, which is consistent with a 7/2− ground state in 157W. Fine structure observed in the α decay of 161Os places the lowest excited state in 157W with Iπ =9/2− at 318±30 keV. The branching ratio of 5.5+3.1 −2.2% indicates that 161Os also has a 7/2− ground state. Shell-model calculations analysing the effects of monopole shifts and a tensor force on the relative energies of 2f7/2 and 1h9/2 neutron states in N=83 isotones are presented.

Design and test of a high-speed flash ADC mezzanine card for high-resolution and timing performance in nuclear structure experiments

This work describes new electronics for the EXOGAM2 (HP-Ge detector array) and NEDA (BC501A-based neutron detector array). A new digitizing card with high resolution has been designed for gamma-ray and neutron spectroscopy experiments. The higher bandwidth requirement of the NEDA signals, together with the necessity for accuracy, require a high sampling rate in order to preserve the shape for real-time Pulse Shape Analysis (PSA). The PSA is of paramount importance for the NEDA to discriminate between neutrons and -ray signals. Both high resolution and high speed parameters are often difficult to achieve in a single electronic unit. These constraints, together with the need to build new digitizing electronics to improve performance and flexibility of signal analysis in nuclear physics experiments, led to the development a new FADC mezzanine card. In this work, the design and development are described, including the characterization procedure and the preliminary measurement results.

A new front-end high-resolution sampling board for the new-generation electronics of EXOGAM2 and NEDA detectors

This paper presents the final design and results of the FADC Mezzanine for the EXOGAM (EXOtic GAMma array spectrometer) and NEDA (Neutron Detector Array) detectors. The measurements performed include those of studying the effective number of bits, the energy resolution using HP-Ge detectors, as well as timing histograms and n/γ discrimination performance. Finally, the conclusion shows how a common digitizing device has been integrated in the experimental environment of two very different detectors which combine both low-noise acquisition and fast sampling rates. Not only the integration fulfilled the expected specifications on both systems, but it also showed how a study of synergy between detectors could lead to the reduction of resources and time by applying a common strategy.

A digital front-end electronics for the neutron detector NEDA

This paper presents the design of the NEDA front-end electronics, a first attempt to involve the use of digital electronics in large neutron detector arrays. Among the electronic modules taking part, we emphasize on the front-end analog processing, the digitalization, digital pre-processing, communications firmware, as well as the integration of the Global Trigger and Synchronization system. The NEDA array will be available for measurements in 2015.

Nuclear Structure far from stability at the N = 50 Shell Closure

Medium and high spin states of the nuclei close to the N = 50 shell closure are investigated using deep inelastic and multi‐nucleon transfer reactions. New excited states of the nuclei 81Ga, 82Ge and 83As at N = 50 shell closure have been identified by means of the 82Se+238U reaction. Gamma rays have been acquired using the PRISMA‐CLARA setup of the Laboratori Nazionali di Legnaro, Italy (LNL).

High-spin study of 162Ta

Excited states in the odd-odd neutron deficient nucleus (162)Ta (Z = 73, N = 89) have been studied for the first time. The gamma spectroscopy analysis using gamma - gamma - gamma coincidences revea ...

Decays of New Nuclides and Isomers Beyond the Proton Drip Line - The Influence of Neutron Configurations

The energy of the vh9/2 orbital in nuclei above N = 82 drops rapidly in energy relative to the vf7/2 orbital as the occupancy of the πh11/2 orbital increases. These two neutron orbitals become nearly degenerate as the proton drip line is approached. In this work, we have discovered the new nuclides 161Os and 157W, and studied the decays of the proton emitter 160Re in detail. The 161Os and 160Re nuclei were produced in reactions of 290, 300 and 310 MeV 58Ni ions with an isotopically enriched 106Cd target, separated in‐flight using the RITU separator and implanted into the GREAT spectrometer. The 161Os α a decays populated the new nuclide 157W, which decayed by β‐particle emission. The β decay fed the known α‐decaying 1/2+ and 11/2− states in 157Ta, which is consistent with a vf7/2 ground state in 157W. The measured α‐decay energy and half‐life for 161Os correspond to a reduced α‐decay width that is compatible with s‐wave α‐particle emission, implying that its ground state is also a vf7/2 state. Over 7000 160Re nuclei were produced and the γ decays of a new isomeric state feeding the πd3/2 level in 160Re were discovered, but no evidence for the proton or a decay of the expected πh11/2 state could be found. The isomer decays offer a natural explanation for this non‐observation and provides a striking example of the influence of the near degeneracy of the vh9/2 and vf7/2 orbitals on the properties of nuclei in this region.The energy of the vh9/2 orbital in nuclei above N = 82 drops rapidly in energy relative to the vf7/2 orbital as the occupancy of the πh11/2 orbital increases. These two neutron orbitals become nearly degenerate as the proton drip line is approached. In this work, we have discovered the new nuclides 161Os and 157W, and studied the decays of the proton emitter 160Re in detail. The 161Os and 160Re nuclei were produced in reactions of 290, 300 and 310 MeV 58Ni ions with an isotopically enriched 106Cd target, separated in‐flight using the RITU separator and implanted into the GREAT spectrometer. The 161Os α a decays populated the new nuclide 157W, which decayed by β‐particle emission. The β decay fed the known α‐decaying 1/2+ and 11/2− states in 157Ta, which is consistent with a vf7/2 ground state in 157W. The measured α‐decay energy and half‐life for 161Os correspond to a reduced α‐decay width that is compatible with s‐wave α‐particle emission, implying that its ground state is also a vf7/2 state. Over 7000 1...

Probing single-particle structures beyond the proton drip line

Single‐particle energies have been investigated in the closed neutron shell proton emitter 155Ta. The 155Ta nuclei were populated through the α decay of 159Re, which has been observed for the first time. The 159Re nuclei were produced in reactions of 300 MeV 58Ni ions with an isotopically enriched 106Cd target, separated in‐flight using the RITU separator and implanted into the GREAT spectrometer. The 159Re α decay emanates from the proton‐emitting πh11/2 state and populates a state in 155Ta which decays by the emission of a proton from a πh11/2 orbital. The results fit in with the systematics of proton and α‐particle separation energies in the region, but disagree with the previously reported decay properties of 155Ta.

Discovery of the proton emitting nucleus 159Re

The observation of the new nuclide 159Re provides important insights into the evolution of single‐particle structure in heavy nuclei beyond the proton drip line. The nuclide 159Re was synthesised in the reaction 106Cd(58Ni,p4n) and identified via its proton radioactivity using the RITU gas‐filled separator and the GREAT focal‐plane spectrometer. Comparisons of the measured proton energy (Ep = 1805±20 keV) and decay half‐life (t1/2 = 21±4 μs) with values calculated using the WKB method indicate that the proton is emitted from an h11/2 state. The implications of these results for future experimental investigations into even more proton unbound Re isotopes using in‐flight separation techniques are considered.

Study of fission fragments produced by 14 N + 235 U reaction

This work was performed to understand the structure of neutron-rich fission fragments around the 130 mass region. A thin 235U target was bombarded by a 14N beam with 10 MeV/A from the Separated Sector Cyclotron at the iThemba Laboratory for Accelerator Based Sciences, Cape Town, South Africa. The main goal was to detect and identify fission fragments and to obtain their mass distribution by using solar cell detectors in the AFRODITE (African Omnipurpose Detector for Innovative Techniques and Experiments) spectrometer. The X-rays emitted from fission fragments were detected by LEP (Low Energy Photon) detectors and γ-rays emitted from excited states of the fission fragments were detected by CLOVER detectors in the spectrometer.