Bulletin of the American Physical Society
2017 Fall Meeting of the APS Division of Nuclear Physics
Volume 62, Number 11
Wednesday–Saturday, October 25–28, 2017; Pittsburgh, Pennsylvania
Session PK: Nuclear Fission II |
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Chair: Anton Tonchev, Lawrence Livermore National Laboratory Room: City Center B |
Saturday, October 28, 2017 10:30AM - 10:42AM |
PK.00001: Study of Photon Emission with the Fission Event Generator $\mathtt{FREYA}$ Ramona Vogt, Jorgen Randrup The event-by-event fission model $\mathtt{FREYA}$\footnote{J.~M.~Verbeke, R.~Vogt and J.~Randrup, Comp. Phys. Comm. {\bf 191}, 178 (2015). $\mathtt{FREYA 2.0.2}$, with the updates discussed here, has also been submitted to Comp. Phys. Comm.} is employed to study photon observables. The model has been expanded beyond the simple statistical photon emission reported previously\footnote{R.~Vogt and J.~Randrup, Phys. Rev. C {\bf 87}, 044602 (2013).} to include the discrete RIPL-3 lines. We update these prior results and discuss the sensitivity of the results to the $\mathtt{FREYA}$ input parameters sensitive to photon observables\footnote{R. Vogt and J. Randrup, in preparation.}. [Preview Abstract] |
Saturday, October 28, 2017 10:42AM - 10:54AM |
PK.00002: Actinide Sputtering Induced by Fission with Ultra-cold Neutrons Tan Shi, Michael Venuti, Deion Fellers, Sean Martin, Chris Morris, Mark Makela Understanding the effects of actinide sputtering due to nuclear fission is important for a wide range of applications, including nuclear fuel storage, space science, and national defense. A new program at the Los Alamos Neutron Science Center uses ultracold neutrons (UCN) to induce fission in actinides such as uranium and plutonium. By controlling the UCN energy, it is possible to induce fission at the sample surface within a well-defined depth. It is therefore an ideal tool for studying the effects of fission-induced sputtering as a function of interaction depth. Since the mechanism for fission-induced surface damage is not well understood, this work has the potential to deconvolve the various damage mechanisms. During the irradiation with UCN, NaI detectors are used to monitor the fission events and were calibrated by monitoring fission fragments with an organic scintillator. Alpha spectroscopy of the ejected actinide material is performed in an ion chamber to determine the amount of sputtered material. Actinide samples with various sample properties and surface conditions are irradiated and analyzed. In this talk, I will discuss our experimental setup and present the preliminary results from the testing of multiple samples. [Preview Abstract] |
Saturday, October 28, 2017 10:54AM - 11:06AM |
PK.00003: A New Measurement of Neutron Induced Fission Cross Sections Joshua Magee Neutron induced fission cross sections of actinides are of great interest in nuclear energy and stockpile stewardship. Traditionally, measurements of these cross sections have been made with fission chambers, which provide limited information on the actual fragments, and ultimately result in uncertainties on the order of several percent. The Neutron Induced Fission ragment Tracking Experiment (NIFFTE) collaboration designed and built a fission Time Projection Chamber (fissionTPC), which provides additional information on these processes, through 3-dimensional tracking, improved particle identification, and in-situ profiles of target and beam non-uniformities. Ultimately, this should provide sub-percent measurements of (n,f) cross-sections. During the 2016 run cycle, measurements of the ^{238}$U(n,f)/$^{235}$U(n,f) cross section shape was performed at the Los Alamos Neutron Science Center (LANSCE) Weapons Neutron Research (WNR) facility. An overview of the fission TPC will be given, as well as these recently reported results. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Saturday, October 28, 2017 11:06AM - 11:18AM |
PK.00004: Modeling the Fission Fragment Detection Efficiency of the NIFFTE fissionTPC Nathaniel Bowden The goal of the Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) is to measure neutron-induced fission cross section ratios with unprecedented precision. The NIFFTE Collaboration has designed and built a Time Projection Chamber, the fissionTPC, for this purpose. The detector enables charged particle tracking with full three-dimensional charge cloud reconstruction, allowing for the characterization of fission fragments originating from a thin central target. Quantifying the fission fragment detection efficiency is a central element of these cross section ratio measurements. Here we describe how the wealth of data captured for every fission event allows us to build and validate a detailed Monte Carlo efficiency model. Effects such as anisotropy, fission fragment energy degradation, and target thickness, composition, and roughness must all be taken into account. [Preview Abstract] |
Saturday, October 28, 2017 11:18AM - 11:30AM |
PK.00005: Preliminary Results from the Triple Fission-Ejecta Correlations Trial (TRIFECTA) at ORNL William Peters, M. S. Smith, A. Galindo-Uribarri, E. Temanson, K. Smith, S. V. Paulauskas, C. Thornsberry, K. L. Jones, R. Grzywacz, J. A. Cizewski Despite fission having been studied for almost 80 years, there is a shortage of data on the correlations of multiple fission products needed to benchmark advanced theoretical models of fission. A pioneering experiment underway at ORNL, the Triple Fission-Ejecta Correlations Trial (TRIFECTA), involves the measurement of energy and angular correlations between prompt $^{\mathrm{252}}$Cf fission neutrons and gamma rays with respect to one fission fragment in time-coincidence. The mass of one fragment is determined, with 4 amu precision, by using 2 micro-channel plate timing detectors and a silicon total-energy detector. Time-coincident data from auxiliary detectors are also recorded: 6 NaI detectors to measure gamma-ray multiplicity, 1 HPGe detector to measure the high-resolution gamma-ray spectrum, and an array of 28 VANDLE modules to measure the neutron spectrum and multiplicity. For the first time, correlations between coincident fragment -- gamma -- neutron fission products can be studied, as a function of fragment mass. Utilizing certain unique gamma-ray transitions recorded by the HPGe detector, we were able to determine the neutron energy and angular correlations of specific fission fragments. Preliminary results on neutron -- neutron angular correlations, gamma-ray vs. neutron multiplicity, and other correlations will be presented, along with plans for future improvements. [Preview Abstract] |
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