125 research outputs found
The pi h(11/2 nu i)(13/2)(-1)(-2) three-hole isomeric state and octupole core excitation in the Tl-205 nucleus
No full textNew high-spin states were identified in the (TI)-T-205 isotope produced in deep-inelastic heavy-ion reactions. The expected 29/2(+) yrast state and 35/2(-) isomeric state with 235 us half-life were located above the 2.6 mus isomer known from previous studies. Above this isomer a 7092 keV level was interpreted as a 41/2(+) state arising from the coupling of the octupole vibration of the Pb-208 core with the three-hole structure of the 35/2(-) isomer
Thermodynamic properties of Au-Fe alloys studied with 57Fe Mössbauer spectroscopy
No full textThe room temperature Mossbauer spectra of 57Fe were measured for Au1.xFex alloys with x in the range 0.01 less-than or equal to x less-than or equal to 0.03. The obtained data were analysed in terms of short range order parameter (SRO) and the binding energy Eb between two iron atoms in the studied materials using the extended Hrynkiewicz-Krolas idea. The estimated negative SRO parameters and the positive binding energy suggest ordering tendencies in Au-Fe alloys at low iron concentration. The extrapolated value of Eb for x = 0 was used for the computation of enthalpy of the solution of Fe in Au. The results were compared with the corresponding data derived from calorimetric measurements, previous Mossbauer experiments and resulting from the cellular atomic model of alloys by Miedema
Decay spectroscopy of 75−79 Cu, 79−81 Zn, and 83−85 Ga
No full textThe beta -decay properties of neutron-rich fission fragments of Cu, Zn, and Ga isotopes were studied at the Holifield Radioactive Ion Beam Facility. Beams of 75-79Cu, 79-81Zn, and 83-85Ga were formed and delivered to two new end-stations at the facility. The Low-energy Radioactive Ion Beam Spectroscopy Station is a traditional on-line low energy (200 keV) beam line with 4 clover Ge detectors, two half-cylindrical plastic \beta -detectors, and a moving tape collector. In addition, many of the beams were accelerated to above 2 MeV/u and delivered to a micro-channel plate and transmission ion chamber located just in front of the same detector setup. In both cases, fine adjustment of an isobar separator was used to enhance the isotope of interest. Excited levels in the daughters and \beta -delayed neutron branching ratios were measured and used to confirm isotope identification. The decays from 79Cu and 85Ga were observed for the first time as was the 84Ge 21+ level populated by \beta and beta n decay channels
Early Signal of Emerging Nuclear Collectivity in Neutron-Rich Sb 129
No full textRadioactive Sb129, which can be treated as a proton plus semimagic Sn128 core within the particle-core coupling scheme, was studied by Coulomb excitation. Reduced electric quadrupole transition probabilities, B(E2), for the 2+ - πg7/2 multiplet members and candidate πd5/2 state were measured. The results indicate that the total electric quadrupole strength of Sb129 is a factor of 1.39(11) larger than the Sn128 core, which is in stark contrast to the expectations of the empirically successful particle-core coupling scheme. Shell-model calculations performed with two different sets of nucleon-nucleon interactions suggest that this enhanced collectivity is due to constructive quadrupole coherence in the wave functions stemming from the proton-neutron residual interactions, where adding one nucleon to a core near a double-shell closure can have a pronounced effect. The enhanced electric quadrupole strength is an early signal of the emerging nuclear collectivity that becomes dominant away from the shell closure
The IFMIF-DONES fusion oriented neutron source: Evolution of the design
No full textIFMIF-DONES is a powerful neutron irradiation facility for the study and qualification of materials planned as part of the European roadmap to fusion-generated electricity. Its main goal is to study properties of materials under severe irradiation in a neutron field similar to the one in a fusion reactor first wall. It is a key facility to prepare for the construction of the DEMO power plant envisaged to follow ITER. The decision to start the construction of IFMIF-DONES is expected imminent. In this paper we present and discuss several key technical studies and decisions to improve and optimize the engineering design of IFMIF-DONES which were carried out as part of the activities in the framework of the EUROfusion Early Neutron Source work package (2015-2020). The following topics are discussed in this paper: the new layout of the IFMIF-DONES SRF LINAC accelerator and high-energy beam transport line, 7Be impurity management approach for the lithium loop, a maintainable test cell concept, a revised layout of the access cell for the remote maintenance operations, and facilities for complementary experiments
gamma-ray spectroscopy of proton neutron-hole nucleus Bi-208 from deep inelastic heavy ion reactions
No full textgamma Rays in the pinu(-1) nucleus Bi-208 have been studied at the Gammasphere using deep-inelastic reactions induced by a 305-MeV Ca-48 beam on a thick Pb-208 target. Previously unknown yrast gamma-ray cascades above the 10(-) millisecond isomer in Bi-208 were identified in cross coincidence with known gamma rays from complementary potassium products. Yrast and near-yrast levels up to 5.6 MeV in Bi-208 have been located, and they are interpreted in light of earlier charged particle spectroscopy results, and with the help of shell model calculations
The IFMIF-DONES Project: Design Status and Main Achievements Within the EUROfusion FP8 Work Programme
No full textInternational Fusion Materials Irradiation Facility-DEMO-Oriented NEutron Source (IFMIF-DONES) is a high-intensity neutron irradiation facility for qualification of fusion reactor materials, which is being designed as part of the European roadmap to fusion-generated electricity. Its main purpose is to study the behavior of materials properties under irradiation in a neutron flux able to simulate the same effects in terms of relevant nuclear responses as those expected in the first wall of the DEMO reactor which is envisaged to follow ITER. It is thus a key facility to support the design, licensing and safe operation of DEMO as well as of the fusion power plants that will be developed afterwards. The start of its construction is foreseen in the next few years. In this contribution, an overview of the IFMIF-DONES neutron source is presented together with a snapshot of the current engineering design status and of the relevant key results achieved within the EUROfusion Work Package Early Neutron Source (WPENS) as part of the 2014–2020 EURATOM Research and Training Programme, complementary to the EU Horizon 2020 Framework Programme (FP8). Moreover, some information on the future developments of the project are given
TRL analysis of IFMIF-DONES
No full textThis work presents an analysis of the IFMIF-DONES design maturity and the necessary activities to increase it up to the level required to launch the procurement phase. The analysis has been performed using a Technology Readiness Level (TRL) methodology. The TRL scale and definitions employed in EU Horizon programs have been found to be appropriate for this assessment, with some modifications to consider the IFMIF-DONES peculiarities. The level of Technology Readiness needed for launching the procurement of each subsystem or component (“target TRL”) has been established. From the comparison between the present TRL and the target TRL, the elements requiring further development and validation have been identified and the experimental activities needed to increase their maturity have been defined. The results of the TRL assessment for the accelerator, lithium and test systems of the facility are presented together with a brief outline of the most relevant validation needs identified
The European approach to the fusion-like neutron source: The IFMIF-DONES project
No full textThe need of a neutron source for the qualification of materials to be used in future fusion power reactors have been recognized in the European (EU) fusion programme for many years. The construction and exploitation of this facility is presently considered to be in the critical path of DEMO. This issue prompted the EU to launch activities for the design and engineering of the IFMIF-DONES (International Fusion Materials Irradiation Facility-DEMO Oriented Neutron Source) facility based on and taking profit of the results obtained in the IFMIF/EVEDA (Engineering Validation and Engineering Design Activities) project, presently conducted in the framework of the EU-Japan Bilateral Agreement on the Broader Approach to Fusion. These activities and R&D work for the IFMIF-DONES Plant are presently taking place in the framework of a work package of the EUROfusion Consortium, in direct collaboration with the Fusion for Energy Organization. The main objective of these activities is to consolidate the design and the underlying technology basis in order to be ready for IFMIF-DONES construction as early as possible. The paper presents the main engineering results for a generic site obtained during the first years of design work, as indicated in the recently released IFMIF-DONES Preliminary Engineering Design Report, making emphasis on the design evolution from previous phases and on the critical issues to be further developed in the near future. The proposed European site to host the facility (Granada, Spain) is briefly introduced as well
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