We report on a gamma-ray coincidence analysis using a mixed array of hyperpure germanium and cerium-doped lanthanum tri-bromide (LaBr3:Ce) scintillation detectors to study nuclear electromagnetic ...transition rates in the pico-to-nanosecond time regime in 33,34P and 33S following fusion–evaporation reactions between an 18O beam and an isotopically enriched 18O implanted tantalum target. Energies from decay gamma-rays associated with the reaction residues were measured in event-by-event coincidence mode, with the measured time difference information between the pairs of gamma-rays in each event also recorded using the ultra-fast coincidence timing technique. The experiment used the good full-energy peak resolution of the LaBr3:Ce detectors coupled with their excellent timing responses in order to determine the excited state lifetime associated with the lowest lying, cross-shell, Iπ=4− “intruder” state previously reported in the N=19 isotone 34P. The extracted lifetime is consistent with a mainly single-particle M2 multipolarity associated with a f7/2→d5/2 single particle transition.
► Half-life measurements of nuclear states. ► Using fast-timing properties of (LaBr3:Ce) scintillator detectors. ► (LaBr3:Ce) scintillation detectors have an excellent timing resolution.
The design of Generation IV nuclear reactors and the research of new fuel cycles require knowledge of the cross sections of different nuclear reactions. Our research is focused on cross section ...measurements of (n,xnγ) reactions occurring in these new reactors. The aim is to measure unknown cross sections and to reduce the uncertainty on present data relative to reactions and isotopes present in transmutation or regeneration processes. The current work consists of studying ^(232)Th(n,n'γ) and ^(235)U(n,xnγ) reactions in the fast neutron energy domain (up to 20 MeV). The experiments are performed at the GEel LINear Accelerator (GELINA) which delivers a pulsed, white neutron beam at IRMM, Belgium. The time characteristics of the beam enable us to measure neutron energies with the time of flight (TOF) technique. The neutron induced reactions (in this case inelastic scattering and (n,2n) reactions) are identified by online prompt γ spectroscopy with an experimental setup including 4 HPGe detectors. A double layered fission chamber is used to monitor the incident neutron flux. The experimental setup and analysis methods will be presented and a comparison between the obtained cross sections and the TALYS predictions will be discussed. This work is a first step in the preparation of the measurement of ^(233)U(n,xnγ) reactions, which are completely unknown at this stage although of very high importance in the ^(232)Th regeneration process. KCI Citation Count: 0
A range of high resolution gamma-ray spectroscopy measurements have been carried out using arrays which include a number of Cerium-doped Lanthanum-Tribromide (LrBr3(Ce)) scintillation detectors used ...in conjunction with high-resolution hyper-pure germanium detectors. Examples of the spectral and temporal responses of such set-ups, using both standard point radioactive sources 152Eu and 56Co, and in-beam fusionevaporation reaction experiments for precision measurements of nuclear excited states in 34P and 138Ce are presented. The current and future use of such arrays at existing (EURICA at RIKEN) and future (NUSTAR at FAIR) secondary radioactive beam facilities for precision measurements of excited nuclear state lifetimes in the 10 ps to 10 ns regime are also discussed.
A method for direct and model-independent measurements of the full cross section for the reaction σ
R
is described, along with the physical setting and the results from measuring σ
R
(
E
) for the ...reaction
6
He+
197
Au in the energy region near the Coulomb barrier. A comparison of cross section values measured by the direct method with a summed cross section of the reaction’s
xn
evaporation channels (
x
= 2–7) and a neutron’s disruption-pickup channels measured by means of activation analysis is presented, along with the familiar value in the literature for a full cross section obtained from processing with an optical model of experimental differential cross sections of the elastic scattering of
6
He on
197
Au.
The low-spin structure of the semimagic 64Ni nucleus has been considerably expanded: combining four experiments, several 0+ and 2+ excited states were identified below 4.5 MeV, and their properties ...established. The Monte Carlo shell model accounts for the results and unveils an unexpectedly complex landscape of coexisting shapes: a prolate 0+ excitation is located at a surprisingly high energy (3463 keV), with a collective 2+ state 286 keV above it, the first such observation in Ni isotopes. The evolution in excitation energy of the prolate minimum across the neutron N=40 subshell gap highlights the impact of the monopole interaction and its variation in strength with N.
A comprehensive set of Monte Carlo simulations was performed with the MCNP5 code to provide a generic characterisation of the neutron and photon fluxes for time-of-flight measurements at all flight ...paths of the GELINA facility. Simulations were performed for the direct flux configuration (DFC, 10
keV–20
MeV) and the moderated flux configuration (MFC, 10
meV–1
MeV). Fluxes and flux energy spectra were obtained for both neutrons and photons. For neutrons, additionally, detailed resolution functions and figures of merit were obtained. The validity of the approach for the photon spectra is shown by comparison with a dedicated measurement. Also, a verification is presented of the validity of the neutron resolution function by comparison with measured capture and transmission data for
103Rh and
56Fe in the incident neutron energy range from 70
eV to 50
keV. This comprehensive overview will facilitate the planning and analysis of measurements at the GELINA facility with an improved knowledge of its physical characteristics.
Ce 140 ( n , γ ) is a key reaction for slow neutron-capture ( s -process) nucleosynthesis due to being a bottleneck in the reaction flow. For this reason, it was measured with high accuracy ...(uncertainty ≈ 5 % ) at the n_TOF facility, with an unprecedented combination of a high purity sample and low neutron-sensitivity detectors. The measured Maxwellian averaged cross section is up to 40% higher than previously accepted values. Stellar model calculations indicate a reduction around 20% of the s -process contribution to the Galactic cerium abundance and smaller sizeable differences for most of the heavier elements. No variations are found in the nucleosynthesis from massive stars. Published by the American Physical Society 2024
The ROSPHERE γ-ray spectroscopy array Bucurescu, D.; Căta-Danil, I.; Ciocan, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2016, Letnik:
837
Journal Article
Recenzirano
The ROmanian array for SPectroscopy in HEavy ion REactions (ROSPHERE) has been designed as a multi-detector setup dedicated to γ-ray spectroscopy studies at the Bucharest 9MV Tandem accelerator. ...Consisting of up to 25 detectors (either Compton suppressed HPGe detectors or fast LaBr3(Ce) scintillator detectors) together with a state of the art plunger device, ROSPHERE is a powerful tool for lifetime measurements using the Recoil Distance Doppler Shift (RDDS) and the in-beam Fast Electronic Scintillation Timing (FEST) methods. The array's geometry, detectors, electronics and data acquisition system are described. Selected results from the first experimental campaigns are also presented.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted) The investigation of the excitation energies of the ... in the neutron-rich Cd isotopes shows an irregular behaviour when approaching ...the neutron shell-closure at N = 82. The energy of the ... in super(128)Cd is lower than the one in super(126)Cd. The transition strength ... in the even isotopes super(122-128)Cd was measured in Coulomb excitation experiments with the high-purity germanium detector array MINIBALL at REXISOLDE (CERN). The values for super(122,124)Cd coincide with beyond-mean-field calculations with a resultant prolate deformation, whereas super(126,128)Cd are better described by shell-model calculations.
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