Bulletin of the American Physical Society
81st Annual Meeting of the APS Southeastern Section
Volume 59, Number 18
Wednesday–Saturday, November 12–15, 2014; Columbia, South Carolina
Session GA: Low Energy Nuclear Physics I |
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Chair: Mark Spraker, University of North Georgia Room: Richland III |
Friday, November 14, 2014 8:30AM - 9:06AM |
GA.00001: TBD Invited Speaker: Mohammad Ahmed |
Friday, November 14, 2014 9:06AM - 9:42AM |
GA.00002: The Future of Transfer Reactions with Stable Beams in the Southeast Invited Speaker: Catherine Deibel Charged-particle spectroscopy is a powerful tool that has been used for decades to accurately and precisely measure properties of excited states in nuclei populated in transfer and charge exchange reactions with stable beams. Typically these measurements are performed in regular kinematics where a light, stable beam impinges on a heavy target and the light reaction particles are momentum analyzed using a spectrograph. These studies have impacted a wide variety of areas in low-energy nuclear physics from tests of shell model predictions [1] to indirect determinations of astrophysical reaction rates [2]. Unfortunately, many of the facilities where these studies were performed have been shut down in recent years and there currently exists a gap in the capabilities to perform charged-particle spectroscopy measurements in the United States. In order to fill this gap, there are several efforts underway to restore spectrographs at University accelerator facilities, including the installation of the Enge split-pole spectrograph, formerly housed at the Wright Nuclear Structure Laboratory at Yale University, at Florida State University's accelerator laboratory. A review of charged-particle spectroscopy and its applications in nuclear physics will be given and plans for the future program with the Yale Enge spectrograph at FSU will be discussed. \\[4pt] [1] J. P. Schiffer {\it et al.}, Phys. Rev. Lett. {\bf 108}, 022501 (2012).\\[0pt] [2] C. M. Deibel {\it et al.}, Phys. Rev. C {\bf 80}, 035806 (2009). [Preview Abstract] |
Friday, November 14, 2014 9:42AM - 10:18AM |
GA.00003: A Novel Method To Distinguish Fissile From Non-Fissile Materials Using Linearly Polarized Gamma-Ray Beams Invited Speaker: Jonathan Mueller We have developed a novel method to distinguish fissile materials, such as those which may be used as fuel in a nuclear reactor or in a nuclear weapon, from non-fissile materials. Our method relies upon using a linearly-polarized $\gamma$-ray beam to induce fission within a sample and then measuring the outgoing fission neutrons. The High Intensity $\gamma$-ray Source (HI$\gamma$S) generated the $\gamma$-ray beams used in our experiments designed to test this novel method. The HI$\gamma$S beam is quasi-monoenergetic and nearly 100\% linearly polarized. We performed photofission experiments using beams from 5.3 to 7.6 MeV on a variety of actinides: $^{232}$Th, $^{233,235,238}$U, $^{237}$Np, and $^{239,240}$Pu. In the fission process, on average 2-4 neutrons are emitted almost simultaneously with the fission event itself; these are known as prompt fission neutrons. An array of 12-18 liquid scintillator neutron detectors was used to measure the ratio of prompt fission neutron yields parallel to the plane of beam polarization to the yields perpendicular to this plane as a function of beam energy. A ratio near one was found for photofission of $^{233,235}$U, $^{237}$Np, and $^{239}$Pu while a significant ratio ($\sim$1.5-3) was found for $^{232}$Th, $^{238}$U, and $^{240}$Pu. This large difference could be used to distinguish fissile isotopes (such as $^{233,235}$U and $^{239}$Pu) from non-fissile isotopes (such as $^{232}$Th, $^{238}$U, and $^{240}$Pu). These ratios are in agreement with a model based on prompt neutron emission in fission and previously measured fission fragment angular distributions. [Preview Abstract] |
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