The Canadian Penning Trap mass spectrometer at the Californium Rare Isotope Breeder Upgrade (CARIBU) facility was used to measure the masses of eight neutron-rich isotopes of Nd and Sm. These ...measurements are the first to push into the region of nuclear masses relevant to the formation of the rare-earth abundance peak at A∼165 by the rapid neutron-capture process. We compare our results with theoretical predictions obtained from "reverse engineering" the mass surface that best reproduces the observed solar abundances in this region through a Markov chain Monte Carlo technique. Our measured masses are consistent with the reverse-engineering predictions for a neutron star merger wind scenario.
Towards commissioning the new IGISOL-4 facility Moore, I.D.; Eronen, T.; Gorelov, D. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
12/2013, Letnik:
317
Journal Article
Recenzirano
•The commissioning of the new IGISOL-4 facility.•First successful implantation of neutron-deficient Pd.•In-jet laser ionization of copper demonstrated.
The Ion Guide Isotope Separator On-Line ...facility at the Accelerator Laboratory of the University of Jyväskylä is currently being re-commissioned as IGISOL-4 in a new experimental hall. Access to intense beams of protons and deuterons from a new MCC30/15 cyclotron, with continued possibility to deliver heavy-ion beams from the K=130MeV cyclotron, offers extensive opportunities for long periods of fundamental experimental research, developments and applications. A new layout of beam lines with a considerable increase in floor space offers new modes of operation at the facility, as well as a possibility to incorporate more complex detector setups. We present a general overview of IGISOL-4 and the current status of several projects, including the collinear laser spectroscopy station and the future of neutron-induced fission. Recent milestones from the first commissioning experiments are presented.
Magnetic films of NiFe permalloy and CoNiFe ternary alloy are used in products of nanoelectronics and microelectronics and in densely packed magnetic memory. NiFe and CoNiFe coatings decrease ...corrosion and wear in electrical devices; they are also used in electrocatalytic materials. Large stresses in magnetic films lead to deformations and the malfunctioning of devices due to peeling of the film from the silicon substrate. In this study, to clarify the nature of the phenomena occurring during the electrochemical deposition of NiFe and CoNiFe films of various thicknesses, which lead to mechanical stresses, investigation of their parameters is carried out. It is demonstrated that measurement of the bending of wafers consisting of Si, SiO
2
, Si
3
N
4
, NiCr, and Ni after the deposition of CoNiFe or NiFe layers on each of them allows determination of the mechanical stresses in the films. It is established that the beinding of the wafers with Si
3
N
4
is negative and greater than that with SiO
2
. The bending after depositing NiCr and Ni layers is negative. The bending of silicon wafers with CoNiFe ternary-alloy films has a maximum value of 180 μm at a film thickness of 12 μm, and that with NiFe films has a maximum value of 150 μm at a film thickness of 15 μm. The bending after depositing NiFe and CoNiFe films is positive. No peeling of the films is observed. The difference in the deformation signs of Ni and CoNiFe or NiFe films and in the direct dependence of the silicon-wafer bending on the thickness of NiFe and CoNiFe films makes it possible to relate the mechanical stresses to hydrogenation (hydrogen embrittlement) and hydrogen release after the process. It is determined that the magnetization of NiFe films is lower than that of triple CoNiFe films. The latter are promising for use in magnetic-field converters.
Singular integral equations of the first and second kind with the Cauchy kernel on a limiting narrow closed contour are theoretically considered. The initial equations are found to become different ...on the limiting contour. This singularity of integral equations with the Cauchy kernel does not allow boundary-value problems of the flow around thin airfoils to be solved correctly; therefore, a system consisting of integral equations of the first and second kind is proposed for solving such problems. The results of the present study are tested against an exact solution of the problem of the flow past a flat plate.
Abstract The capability to directly study neutron capture reactions on radionuclides with half-lives on the of order minutes would allow key cross section measurements in nuclear astrophysics and ...energy applications. However, such experiments with stationary targets are currently impossible because of signal detection and target sample fielding issues. To overcome these challenges, a neutron target facility is being developed to permit neutron capture experiments on unstable isotopes in inverse kinematics at the Los Alamos Neutron Science Center (LANSCE). This next-generation facility will consist of a heavily moderated, high-intensity spallation neutron target coupled with a radioactive ion beam storage ring. A proof-of-principle experiment is underway to demonstrate this neutron target concept at LANSCE in the near term with stable ions and without a storage ring. Here, mA-level beams of 10-50 keV heavy ions exhibiting large resonant neutron capture cross sections will be generated by a new ion source, transported through a large-volume neutron moderator surrounding an adjacent spallation target driven by the LANSCE accelerator, and collected downstream of the moderator for subsequent decay-counting measurements. The neutron density within the moderator will be obtained from these decay yields and compared with Monte Carlo N-Particle (MCNP) simulation results. The science application, operational requirements, and performance objectives for this heavy ion source will be presented.
Abstract
The LANSCE accelerator facility has been in operation for 50 years performing important scientific support for national security. The unique feature of the LANSCE accelerator facility is ...multi-beam operation, delivering beams to five experimental areas. To reduce long-term operational risks and to realize future beam performance goals in support of the laboratory missions, we are developing a novel high-brightness Front End injector. The proposed injector includes two independent low-energy transports for H
+
and H
-
beams merging beams at the entrance of a single RFQ. These beamlines also perform preliminary beam bunching before RFQ. The challenge of the present project is associated with the simultaneous acceleration of protons and H
-
ions with multiple beam flavors in a single RFQ, which has never been done before. The proposed injector must provide better than existing beam parameters while beam intensity is supposed to be increased by a factor of two and injection energy is reduced from 750 keV to 100 keV. The paper discusses the details of the design and presents injector parameters.
In this article a comprehensive description and performance of the double Penning-trap setup JYFLTRAP will be detailed. The setup is designed for atomic mass measurements of both radioactive and ...stable ions and additionally serves as a very high-resolution mass separator. The setup is coupled to the IGISOL facility at the accelerator laboratory of the University of Jyväskylä. The trap has been online since 2003 and it was shut down in the summer of 2010 for relocation to the upgraded IGISOL facility. Numerous atomic mass and decay energy measurements have been performed using the time-of-flight ion-cyclotron resonance technique. The trap has also been used in several decay spectroscopy experiments as a high-resolution mass filter.
We report the first experimental determination of independent isomeric yield ratios using direct ion counting with a Penning trap, which offered such a high resolution in mass that isomeric states ...could be separated. The measurements were performed at the Ion Guide Isotope Separator On-Line (IGISOL) facility at the University of Jyvaskyla. The isomer production ratios of Ge-81, Y-96,Y-97 Sn-128(,1)30, and Sb-129 in the 25-MeV proton-induced fission of U-na(t) and Th-232 were studied. Three isomeric pairs (Ge-81, Y-96, and Sb-129) were measured for the first time for the U-na(t)(p, f) reaction, while all the reported yield ratios for the Th-232(p, f) reaction were determined for the first time. The comparison of the experimentally determined isomeric yield ratios with data available in the literature shows a reasonable agreement, except for the case of Sn-130 for unspecified reasons. The obtained results were also compared with the GEF model, where good agreement can be noticed in most cases for both reactions. Serious discrepancies can only be observed for the cases of Y-96(,)97 for both reactions. Moreover, based on the isomeric yield ratios, the root-mean-square angular momenta (J(r)(ms)) of the fission fragments after scission were estimated using the TALYS code. The experimentally determined isomeric yield ratios, and consequently the deduced J(rms), for Sn-130 are significantly lower compared to Sn-128 for both fissioning systems. This can be attributed to the more spherical shape of the fragments that contribute to the formation of Sn-130, due to their proximity to the N = 82 shell closure. The values of J(rms) for Sb-129 are higher than Sn-128 for both reactions, despite the same neutron number of both nuclides (N = 78), indicating the odd-Z effect where fission fragments with odd-Z number tend to bear larger angular momentum than even-Z fragments. The isomer production ratio for the isotopes of Sn is more enhanced in the U-na(t)(p, f) reaction than in Th-232(p, f). The opposite is observed for Y-96 and Y-97. These discrepancies might be associated to different scission shapes of the fragments for the two fission reactions, indicating the impact that the different fission modes can have on the isomeric yield ratios.
To enhance the production of medium-heavy, neutron-rich nuclei, and to facilitate measurements of independent yields of neutron-induced fission, a proton-to-neutron converter and a dedicated ion ...guide for neutron-induced fission have been developed for the IGISOL facility at the University of Jyväskylä. The ion guide holds the fissionable targets, and the fission products emerging from the targets are collected in helium gas and transported to the downstream experimental stations. A computer model, based on a combination of MCNPX for modeling the neutron production, the fission code GEF, and GEANT4 for the transport of the fission products, was developed. The model will be used to improve the setup with respect to the production and collection of fission products. In this paper we benchmark the model by comparing simulations to a measurement in which fission products were implanted in foils located at different positions in the ion guide. In addition, the products from neutron activation in the titanium foil and the uranium targets are studied. The result suggests that the neutron flux at the high-energy part of the neutron spectrum is overestimated by approximately 40
%
. However, the transportation of fission products in the uranium targets agrees with the experiment within 10
%
. Furthermore, the simulated transportation of fission products in the helium gas achieves almost perfect agreement with the measurement. Hence, we conclude that the model, after correction for the neutron flux, is well suited for optimization studies of future ion guide designs.
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