Program - Brookhaven National Laboratory

law of the temperature ratio (RT = TL/TH, with TL and TH the temperature of the light and heavy
fragment) has been proposed. With this RT -law, the main fission observables of the 252 Cf(sf) could be
reproduced. Here, in order to take into account the fission modes by which the fissioning nucleus undergoes
to fission, we have adopted a specific RT -law for each fission mode. For actinides, the two main fission
modes are called Standard I and Standard II (following the Brosas’s terminology [2]). This new procedure
has been applied on various spontaneously fissioning Pu-isotopes, since a strong variation of the relative
importance of both modes appear for these isotopes [3]. The Pu-isotopes constitute therefore a nice
database to investigate the impact of fission modes on the prompt fission neutron observables (multiplicity
and spectra).
[1] O. Litaize and O. Serot, Phys. Rev. C 82, 054616 (2010) [2] U. Brosa, S. Grossman and A. Muller,
Phys. Rep. 197 (1990) 167 [3] L. Demattè et al., Nucl. Phys. A 617 (1997) 331-346
PR 70
Consistent Modeling of (n, f), (γ, f) and (t, pf) Cross Sections
P. Talou, J.E. Lynn, Nuclear Physics Group, Theoretical Division, Los Alamos National Laboratory, Los
Alamos, NM 87545, USA. O. Bouland, Physics Studies Laboratory, CEA, DEN, DER, SPRC,
Cadarache, F-13108 Saint-Paul-lez-Durance, France.
An accurate and consistent theoretical prediction of fission cross sections remains a daunting task to
this day, as many model parameters are often tuned to accurate experimental data, when known, and
crudely extrapolated when data is missing. Chief among those parameters are the fission barrier heights
and widths, and the level densities at the saddle points. The specific model used to describe fission
probabilities can dramatically change the choice of those parameters and render difficult a clear comparison
with experimental fission barriers, for instance. Here we present an attempt to describe several fission cross
section data, leading to the same fissioning nucleus, such as (n, f), (γ, f), (t, pf), as well as fission fragment
angular distributions, consistently, i.e., within a unified model with a single and common set of model
parameters. Fission probabilities are calculated in the R-matrix formalism applied to the main fission
channel [1], paying particular attention to the intermediate structures generated by the presence of states
in the second-well of the fission path. Treating the specific entrance channel correctly is also very important
as it determines which fission transition states are more likely to contribute. For instance, neutron-induced
fission and transfer reaction leading to fissions will populate distinct spin and parity sub-spaces in the
fissioning nucleus, leading to significant corrections in the fission probabilities. We will present preliminary
results in the case of 236 U ∗ fissioning system, for which available experimental data on different reaction
channels can be used to constrain the model calculations.
[1] J.E. Lynn, J. Phys. A: Math., Nucl. Gen., 6 (1973) 542.
PR 71
Teaching Quantum Mechanics with Single-Photon Experiments
Charles Baily, University of Colorado at Boulder.
A common learning goal for instructors of advanced physics is for students to recognize a difference between
the experimental uncertainty of classical physics and the fundamental uncertainty of quantum mechanics.
We have documented the positive impact on student thinking of incorporating experiments on the
foundations of quantum mechanics into the undergraduate physics curriculum. In light of the Advanced
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