Bulletin of the American Physical Society
2010 Annual Meeting of the California-Nevada Section of the APS
Volume 55, Number 12
Friday–Saturday, October 29–30, 2010; Pasadena, California
Session C3: Nuclear, High Energy and Accelerator Physics I |
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Chair: Jennifer Klay, California Polytechnic State University, San Luis Obispo Room: Building 17 - Cahill Center for Astronomy and Astrophysics, Hameetman Auditorium |
Friday, October 29, 2010 2:00PM - 2:12PM |
C3.00001: Nuclear constraints on properties of rotating neutron stars and gravitational waves Plamen Krastev, Bao-An Li Nuclear reactions with radioactive beams provide unique means to constrain the equation of state (EOS) of neutron-rich matter, in particular its density dependence through the nuclear symmetry energy. The EOS is important for our understanding of numerous phenomena in nuclear physics, astrophysics and cosmology. Applying an EOS with symmetry energy constrained by recent nuclear laboratory data, we set a limit on the properties of rotating neutron stars and the resultant gravitational waves. [Preview Abstract] |
Friday, October 29, 2010 2:12PM - 2:24PM |
C3.00002: Fragment Angular Distribution for Neutron Fission of 232Th and 238U A.N. Behkami, S. Rasuli The fragment angular distribution data are crucial to the interpretation of the sub-barrier resonances. Recently structure is reported in neutron induced fission fragment angular distributions of even-even actinide nuclei near threshold. The fission fragment angular distributions of $^{232}$Th and $^{238}$U exhibit considerable structure in the vicinity of fission threshold. The energy dependence of fission fragment angular anisotropies for $^{232}$Th (n, f) and $^{238}$U (n, f) reactions have been calculated in the frame work of statistical model. The results have been compared with existing experimental data taken from the library of experimental nuclear reaction data (EXFOR). We have found that the periodic structure of anisotropy related to the set of (n, xn) reaction is not extended beyond the threshold of (n,4n) reaction at incident neutron energy En$\sim $25MeV. Above this a smooth decrease of fragment anisotropies is observed at higher neutron energies, results will be presented and discussed. [Preview Abstract] |
Friday, October 29, 2010 2:24PM - 2:36PM |
C3.00003: An overview of the Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) including first detector performance results Rich Baker NIFFTE is an exciting new project to make high precision measurements of nuclear fission cross sections using a time projection chamber (TPC). These measurements are expected to enable significant advances in nuclear reactor design and advanced fuel cycle efforts. In my talk, I will give an overview of the physics goals of the experiment and explain how we plan to achieve these goals with the NIFFTE TPC. I will also discuss the current status of the project and present some first detector performance results from data taken this summer and fall. [Preview Abstract] |
Friday, October 29, 2010 2:36PM - 2:48PM |
C3.00004: The NIFFTE Time Projection Chamber Gas Handling System Assembly Dana Duke The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) uses a Time Projection Chamber (TPC) to obtain more accurate measurements of the fission cross sections of radioactive isotopes such as Pu-239, U-235, U-238, etc. Past cross section measurements have used various detection methods, but by using current TPC technology, accuracy levels can be improved to sub 1\% error. Analysis of TPC data will improve the current understanding of fission dynamics and of the fission process. A summary of time projection chamber operations is given. The NIFFTE TPC is located at the 90L flight path at LANSCE-WNR where targets are bombarded with fast neutrons to induce fission. The resulting fission fragments are tracked using gas ionization within the TPC. Gas Handling system function and assembly is examined and justified. Major system components are discussed. [Preview Abstract] |
Friday, October 29, 2010 2:48PM - 3:00PM |
C3.00005: Software and computing for NIFFTE: updates and current status Ryuho Kudo The Neutron Induced Fission Fragment Tracking Experiment will employ a novel, high granularity, pressurized time projection chamber to measure fission cross-sections of the major actinides to sub-1\% precision. Over the past year, as the experiment has progressed to data collection, many crucial software and computing components have been updated and/or completed. This talk will review the current status of the online software and data acquisition environment being employed at LANSCE and several improvements to offline reconstruction. Future plans will also be presented. [Preview Abstract] |
Friday, October 29, 2010 3:00PM - 3:12PM |
C3.00006: Three Dimensional Photonic Crystal Particle Accelerators Chris McGuinness Laser driven dielectric accelerator structures have recently become of interest due to the potential GeV/m accelerating gradients, high efficiency, low costs associated with large scale lithographic fabrication, and attosecond bunch lengths in such accelerating schemes. Photonic crystals provide an attractive way to confine laser radiation, allowing for the manipulation of the EM fields without the use of metallic boundaries. One structure that has been explored to this end is the woodpile structure. This structure is attractive because it has a fully three-dimensional bandgap, is amenable to common lithographic procedures, and allows for the design of additional accelerator components such as couplers and focusing fields. An eight and nine layer woodpile structure with a defect designed to support an accelerating mode has been fabricated. The structures were fabricated using a combination of nanofabrication techniques that will be described. Limits imposed by the optical lithography set the minimum feature size to 400~nm, corresponding to a structure with a bandgap centered at 4.26~$\mu$m. Reflection spectroscopy measurements reveal a peak in reflectivity about the predicted region, and good agreement with simulation is shown. [Preview Abstract] |
Friday, October 29, 2010 3:12PM - 3:24PM |
C3.00007: Photoproduction of the Cascade Hyperons at Jefferson Laboratory Harneet Grewal, John Price The $\Xi$, or ``Cascade'' hyperon, is related to the proton by $\mathrm{SU}(3)_F$ symmetry. This means that their properties are expected to be related to one another, as are the properties of their respective excited states. This hints at the possibility of using the excited states in the $\Xi$ spectrum to learn more about the excited states of the nucleon, which are hard to isolate in the laboratory due to their large widths. A systematic study of the excited states of the Cascade has been initiated at the Thomas Jefferson National Accelerator Facility (``Jefferson Lab'', or ``JLab'') to map out the excited Cascade spectrum using the process $\gamma p\to K^+K^+\Xi^-$, which can in principle be used to look at the entire Cascade spectrum. This talk will present the motivations for this study, the current status of our work, and an outlook for the future. [Preview Abstract] |
Friday, October 29, 2010 3:24PM - 3:36PM |
C3.00008: Hyperon Rescattering processes with CLAS Alec Thompson, John Price The recent finding of a large production rate for the process $\gamma p\to K^+K^+\Xi^-$ at JLab has opened up the possibility of using the produced $\Xi^-$ as a tagged beam with which to study the $\Xi^-p$ scattering process. This process should be related to the $pp$ cross section by $\mathrm{SU}(3)_F$ symmetry. It is important to the hypernuclear community, as one of the building blocks in the production of $\Xi$-enriched hypernuclear states, which is in turn important to the astrophysical community for its implications on the study of the behavior of nuclear matter at varying densities. Under the proper circumstances, the process $\Xi^-p\to\Lambda\Lambda$ may be used to directly measure the parity of the ground-state $\Xi$, which has not yet been done. This talk will present the motivation behind this study, and the initial results of this study in $\Lambda p$ scattering. [Preview Abstract] |
Friday, October 29, 2010 3:36PM - 3:48PM |
C3.00009: Improving Kaon identification with CLAS Ruben Medina, John Price The JLab program in Cascade physics is based on the process $\gamma p\to K^+K^+\Xi^-$. As such, it is critically dependent on efficient,reliable kaon identification. The largest background for this reaction is uncorrelated events in which one of the $K^+$ particles (or both) is actually a $\pi^+$ which has been misidentified due to its high momentum. This talk will outline the various methods currently used to separate pions from kaons, and will discuss the techniques currently being developed to extract the best possible kaon identification from our existing data set, as well as possibilities for the future. [Preview Abstract] |
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