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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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453 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

Direct reaction techniques are powerful tools to study the single-particle nature of nuclei. Performing direct reactions on short-lived nuclei requires radioactive ion beams produced either via fragmentation or the Isotope Separation OnLine (ISOL) method. Some of the most interesting regions to study with direct reactions are close to the magic numbers where changes in shell structure can be tracked. These changes can impact the final abundances of explosive nucleosynthesis. The structure of the chain of tin isotopes is strongly influenced by the Z = 50 proton shell closure, as well as the neutron shell closures lying in the neutron-rich, N = 82, and neutron-deficient, N = 50, regions. Here, we present two examples of direct reactions on exotic tin isotopes. The first uses a one-neutron transfer reaction and a low-energy reaccelerated ISOL beam to study states in Sn-131 from across the N = 82 shell closure. The second example utilizes a one-neutron knockout reaction on fragmentation beams of neutron-deficient Sn- 106,108 Sn. In conclusion, In both cases, measurements of γ rays in coincidence with charged particles proved to be invaluable.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1987

Large negative Ti-50 anomalies in refractory inclusions from the Murchison carbonaceous chondrite - Evidence for incomplete mixing of neutron-rich supernova ejecta into the solar system

An ion microprobe was used to measure Ti-50 variations in hibonite-rich inclusions from the Murchison chondrite. Both deficits and excesses of the isotope were found, depending on the inclusion being scanned. The anomalies were not correlated with the mineralogy, chemical composition, other isotopic anomalies of Ti, etc. The lack of correlations indicates that the cosmic chemical memory model (Clayton, 1981) cannot explain the observed variations. The Ti-50 concentrations may have originated when a supernova explosion triggered the collapse of a molecular cloud that formed the solar system. The solar system Ti-50 anomalies were from the cloud, not the progenitor star.

Hinton, Richard W.↗
DOE OSTI2014

FRIB Fragment Pre-separator Radiation Environment Studies - Paper 133

The Facility for Rare Isotope Beams (FRIB), a project supported by the US DOE Office of Science, is under construction at Michigan State University. The project will use projectile fragmentation and induced in-flight fission of heavy ion beams at energies of 200 MeV/u and higher, and at a beam power of 400 kW, to produce rare isotope beams for nuclear physics experiments. The production of rare isotope beams during FRIB operations creates a high radiation environment in the fragment pre-separator area where the production target is located. Adequate shielding must be placed around the beam line components to ensure personnel protection during and after the operations. Detailed radiation transport studies in the fragment pre-separator area are necessary and have been performed for proper shielding choices. We calculate neutron and photon fluxes and their energy distributions, and evaluate prompt and residual dose equivalent rates in the hot cell and prompt dose equivalent rates in the MSM gallery outside of the cell where people might be present during normal operations. We also calculate dose equivalent rates in the MSM gallery when the activated components are placed in front of the MSM lead glass window on the hot cell side. We show that the resulting dose equivalent rates are conservative even for the most neutron-rich energetic beams. These calculations guide local shielding design and support operations. (authors)

43 PARTICLE ACCELERATORS↗