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Proposal for precision determination of 7.8 eV isomeric state in229Th at heavy ion storage ring
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">The ultraviolet optical transition of the isomeric state in Th-229 has attracted much attention recently due to its potential application to building an atomic/nuclear clock with ultra-high precision. However, the lowest nuclear excitation energy and the lifetime of the first excited state of Th-229 were not measured directly and precisely until now, and how to precisely determine this isomer state of the Th-229 is an urgent requirement. Here an experimental approach of using a technique similar to that of dielectronic recombination to measure the transition energy of the isomer state of Th-229 at heavy ion storage rings is described. It is expected that the resonant transition can be found and determined with a precision better than several milli-eV.</span
Diffusion of Ag, Au and Cs implants in MAX phase Ti3SiC2
No full textMAX phases (M: early transition metal; A: elements in group 13 or 14; X: C or N), such as titanium silicon carbide (Ti3SiC2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti3SiC2 has been considered as a possible fuel cladding material. This study reports on the diffusivities of fission product surrogates (Ag and Cs) and a noble metal Au (with diffusion behavior similar to Ag) in this ternary compound at elevated temperatures, as well as in dual-phase nanocomposite of Ti3SiC2/3C-SiC and polycrystalline CVD 3C-SiC for behavior comparisons. Samples were implanted with Ag, Au or Cs ions and characterized with various methods, including X-ray diffraction, electron backscatter diffraction, energy dispersive X-ray spectroscopy, Rutherford backscattering spectrometry, helium ion microscopy, and transmission electron microscopy. The results show that in contrast to immobile Ag in 3C-SiC, there is a significant outward diffusion of Ag in Ti3SiC2 within the dual-phase nanocomposite during Ag ion implantation at 873 K. Similar behavior of Au in polycrystalline Ti3SiC2 was also observed. Cs out-diffusion and release from Ti3SiC2 occurred during post-implantation thermal annealing at 973 K. This study suggests caution and further studies in consideration of Ti3SiC2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures. (C) 2015 Elsevier B.V. All rights reserved
Study of projectile fragmentation reaction with isochronous mass spectrometry
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Relative yields of fragments following the Kr-78 projectile fragmentation in a beryllium target were measured in a storage ring by using isochronous mass spectrometry (IMS). Odd-even staggering of the relative fragment yields is observed and can be explained by the odd-even staggering of the particle-emission threshold energies. IMS is a complementary technique to gamma-ray spectroscopy for measuring isomeric ratios, in particular for nuclides with long lifetimes. It was found that the isomeric yield ratios in Fe-53 are almost constant for different longitudinal momenta.</span
Double-peak structures in transmission of H2+ ions through conical multicapillaries in a polymer: Projectile-energy dependence
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Transmission experiments of 7-200 keV H-2(+) ions through conical multicapillaries with inlet or outlet diameters of 4/2 mu m and a length of 30 mu m etched in a PC polymer are reported. The yield of the transmitted particles as a function of the capillary tilt angle was measured. The results show that for 200 keV H-2(+) ions the guiding effect disappears but a focusing effect is obtained with a density enhancement factor of 3.5. For 7-50 keV H-2(+) ions their transmitted particle curves exhibit a pair of shoulder peaks on the left-and right-hand side of the center angle 0 degrees. As the ion energy increases, the shoulder-peak structure is found to vanish leaving one peak at 0 degrees.</span
Direct mass measurements of neutron-rich ~(86)Kr projectile fragments and the persistence of neutron magic number N=32 in Sc isotopes
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">In this paper, we present direct mass measurements of neutron-rich Kr-86 projectile fragments conducted at the HIRFL-CSR facility in Lanzhou by employing the Isochronous Mass Spectrometry (IMS) method. The new mass excesses of 52-54SC nuclides are determined to be -40492(82), -38928(114), -34654(540) keV, which show a significant increase of binding energy compared to the reported ones in the Atomic Mass Evaluation 2012 (AME12). In particular, Sc-53 and Sc-64 are more bound by 0.8 MeV and 1.0 MeV, respectively. The behavior of the two neutron separation energy with neutron numbers indicates a strong sub-shell closure at neutron number N=32 in Sc isotopes.</span