Program - Brookhaven National Laboratory

Methods have been developed to extrapolate measured first-chance fission-product yields and average fragment
total kinetic energies to higher incident-neutron energies where second, third, and forth chance fission
are of importance. The yields for fragment mass near the asymmetric peaks at A 100 and A 138 decrease
with increasing incident-neutron energy, while the yields for symmetry fragments, and fragments with
masses less than A 96 and more than A 146 increase with increasing incident-neutron energy. Predictions
are made for the energy dependence of plutonium fission-product yields. These are compared to the limited
available data. A prediction is made for the average total kinetic energy of 239 Pu(n,f) fission fragments,
up to a neutron energy of 20 MeV. These predictions will be tested in the next few years by the SPIDER
collaboration at Los Alamos.
Session DA Neutron Cross Section Measurements
Monday March 4, 2013
Room: Met East at 3:30 PM
DA 1 3:30 PM
The Fission Time Projection Chamber Project
Tony Hill, the NIFFTE Collaboration
INL
New high-precision fission experiments have become a priority within the low-energy nuclear community.
Modern sensitivity calculations have revealed unacceptable liabilities in some of the underlying fundamental
nuclear data and have provided target accuracies for new measurements that are well beyond what can
be delivered using current experimental technologies. A potential breakthrough in the precision barrier
for these measurements is the deployment of a Time Projection Chamber (TPC). TPC detector systems
were originally developed within the particle physics community and have played a central role in that
field for nearly 25 years. A group of 6 universities and 4 national laboratories have undertaken the task of
building the first TPC designed specifically for the purpose of measuring fission cross sections. In this talk,
I will present the motivation for the fission TPC concept, a few details of the device and why we think an
improvement on 50 years of fission experiments can be accomplished.
DA 2 4:00 PM
Measuring the α/SF Branching Ratio of 252 Cf with the NIFFTE Time Projection Chamber
Lucas Snyder, the NIFFTE Collaboration
LLNL
Fission reactions are particularly complicated quantum systems and current nuclear theory lacks the necessary
predictive power to calculate many of the fundamental quantities associated with the process. The
neutron induced fission cross section is one experimentally measured value of particular importance in the
calculation and simulation of nuclear fuel cycles. The NIFFTE collaboration is developing a fission Time
Projection Chamber intended to measure energy dependent neutron induced fission cross sections of the
major and minor actinides to an uncertainty of better than 1%. The fission TPC will address many of the
systematic uncertainties associated with past and current detector systems used to measure the neutron
induced fission cross section by providing detailed 3-dimensional images of ionizing particles such as fission
fragments and alpha particles. To establish the particle tracking and identification abilities of the fission
TPC in the development phase, the α-decay and spontaneous fission of 252 Cf was observed with a partial
TPC. Preliminary results of an analysis of the α/SF branching ratio of 252 Cf will be presented.
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