Program - Brookhaven National Laboratory

y the emitted neutron. The Versatile Array of Neutron Detectors at Low Energy (VANDLE) [1] was
commissioned at the Holifield Radioactive Ion Beam Facility (HRIBF). The HRIBF used proton-induced
fission of 238 U to produce intense and high isotopic purity beams of neutron-rich nuclei. Neutron energy
spectra in key regions of the nuclear chart were measured near the shell closures at 78 Ni and 132 Sn, and for
the deformed nuclei near 100 Rb. Many of the studied nuclei lie directly on proposed r-process paths. Of the
almost thirty βn emitters studied, only a few relatively long-lived isotopes were previously investigated.
For some of the most exotic nuclei, narrow and intense peaks in the neutron energy distribution indicate
the presence of resonances, which are most likely signatures of the excitation of “core” states. In several
cases, relatively high-energy neutrons are observed. Selected results will be presented. This research
was sponsored in part by the National Nuclear Security Administration under the Stewardship Science
Academic Alliances program through DOE Cooperative Agreement No. DE-FG52-08NA28552
[1] C. Matei et al., Proceedings of Science, NIC X, 138 (2008)
OE 2 2:00 PM
A New Approach to Estimating the Probability for β Delayed Neutron Emission
E.A. McCutchan, A.A. Sonzogni, T.D. Johnson
Brookhaven National Laboratory
The probability for emitting a neutron following β decay, Pn, is critical in many areas of nuclear science
from understanding nucleosynthesis during the r-process to control of reactor power levels and waste
management. As the Pn value is an observable which is not trivial to measure or calculate, indirect
empirical approaches have attempted to characterize measured Pn values based on the total Q value of the
decay and the neutron separation energy, Sn, in the daughter nucleus and from these systematics provide
estimates of Pn values in unexplored regions of the nuclear chart. A new approach to Pn systematics
will be described which incorporates the half-life of the decay and the Q value for the β-delayed neutron
emission. This prescription correlates the known data better and thus improves the estimation of Pn values
for neutron-rich nuclei. Such an approach can be applied to generate input values for r-process network
calculations or in the modeling of advanced fuel cycles. The possibility that these systematics can reveal
information on the β-strength function to levels above the neutron separation energy will also be explored.
Work supported by the DOE Office of Nuclear Physics under Contract No. DE-AC02-98CH10946.
OE 3 2:20 PM
Beta-delayed Neutron Spectroscopy with Trapped Ions
N.D. Scielzo, R.M. Yee, S. Padgett, M. Pedretti, Lawrence Livermore National Laboratory. A.
Czeszumska, E.B. Norman, University of California, Berkeley. P.F. Bertone, J.A. Clark, J.P. Greene,
A.F. Levand, A. Perez Galvan, G. Savard, B.J. Zabransky, Argonne National Laboratory. S.A. Caldwell,
M.G. Sternberg, J. Van Schelt, University of Chicago. D. Lascar, R.E. Segel, Northwestern University.
K.S. Sharma, University of Manitoba. F. Buchinger, S. Gulick, G. Li, McGill University. C.M. Deibel,
Louisiana State University.
Neutrons emitted following the β decay of fission fragments play an important role in many fields of basic
and applied science such as nuclear energy, nuclear astrophysics, and stockpile stewardship. However, the
nuclear data available today for individual nuclei is limited for the vast majority of neutron emitters, the
energy spectrum has not been measured and some recent measurements have uncovered discrepancies as
large as factors of 2-4 in β-delayed neutron branching ratios. Radioactive ions held in an ion trap are
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