Bulletin of the American Physical Society
Annual Meeting of the APS Four Corners Section
Volume 60, Number 11
Friday–Saturday, October 16–17, 2015; Tempe, Arizona
Session K8: Nuclear Physics II |
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Chair: Matthias Burkhardt, New Mexico State University Room: PSF166 |
Saturday, October 17, 2015 1:12PM - 1:24PM |
K8.00001: Americium activated scintillators Alec Raymond, J. Bart Czirr, John E. Ellsworth We are interested in studying the useful lifetime of americium activated plastic and glass scintillators used as calibration and reference sources. The light output per decay event decreases over time as a result of radiation damage to the scintillating material. Reported here is the measured light output of 25-year-old americium activated glass and plastic scintillators and our experimental setup to further study the degradation of scintillators. [Preview Abstract] |
Saturday, October 17, 2015 1:24PM - 1:36PM |
K8.00002: Response Magnitude Uniformity of Two Commercial 5'' Photomultiplier Tubes John Peterson, John E. Ellsworth, Lawrence B. Rees, Michael Ware We are investigating the magnitude of the signal response of two photomultiplier tubes, the Hamamatsu R1250 and the Adit B133D01, to characterize the response across the full spatial extent of each tube. The tubes are mounted on translational stages to direct an attenuated light pulse through a pinhole onto regularly spaced regions of the photocathode. Each pulse is simultaneously measured by a fast photodiode to be used as a reference for the magnitude of the photomultiplier tube response. Peak and area responses will both be considered. Together with the timing characteristics previously studied, this research will provide a more complete description of the response characteristics of these photomultiplier tubes across the entire photocathode. [Preview Abstract] |
Saturday, October 17, 2015 1:36PM - 1:48PM |
K8.00003: Measuring the Proton Range In-Vivo Using Prompt Gamma-Rays Jason Holmes, David Blyth, Ricardo Alarcon, Martin Bues, Mirek Fatyga Proton range uncertainty remains one of the most severe limiting factors in proton beam therapy (PBT). In this work we aim to reduce proton range uncertainty by measuring proton range during patient treatment. To measure the proton range, a collimated gamma detector array is being designed. An MCNPX simulation was first conducted which suggested the feasibility of such a design to measure the Bragg Peak with an uncertainty of 2 to 4 mm per spot. Many studies pertaining to the feasibility of in-vivo proton range verification via detection of prompt gamma radiation have been performed, but designing detectors for clinical use remains challenging. During patient treatment, fast neutrons generated in the PBT equipment, the patient and the detector produce significant background signal to the prompt gamma signal. Time of flight (TOF) has been shown to be a feasible method for eliminating the late arriving neutrons, however this method only applies to proton beams with well-defined timing information. Pulse shape discrimination (PSD) in thin CsI (Tl) scintillation crystals is being investigated as an alternative method to discriminate the neutron background. In this presentation, an update on the progress will be given focusing mainly on the PSD results so far. [Preview Abstract] |
Saturday, October 17, 2015 1:48PM - 2:00PM |
K8.00004: Paired Scission Neutrons KaeCee Terry, John E Ellsworth, Lawrence Rees During fission of heavy nuclei, neutrons are emitted from the fission fragments and the scission point. It is postulated that scission neutrons can be emitted in pairs. This correlation may lead to a better understanding of the spatial and temporal characteristics of the nuclear fission process. With the use of Time of Flight techniques and capture-gated detectors, paired neutrons may be observable. Reported here are our efforts at BYU to investigate these paired neutrons by utilizing a Lithium-Gadolinium-Borate detector and specifically developed analytical code. [Preview Abstract] |
Saturday, October 17, 2015 2:00PM - 2:12PM |
K8.00005: Nuclear Quantum Mechanics may be Analyzed Balancing Neutrinos against Gamma Rays Richard Kriske Xenon 135 is the strongest absorber of Neutrons known with a cross-section of two-million Barns. It has a half-life of 9.2 hours. When it absorbs a Neutron it decays into Xe-136 and if not it decays into Cs-135. It may be possible to keep Xe 135 a superposition state using a Gamma Ray or X-ray Laser. In the Superposition state the Xe 135 itself acts as a Laser of sorts, a Neutron Laser, in that it could produce Neutrons as an output using Superposition as Lasers do, and be pumped by a Gamma or X-ray Laser, a sort of compound Laser. It also reveals a problem in QED, and as a result all of Particle Physics. Particle Physics is based on a Deduction-from-Conclusion first put forward by Feynman. Feynman believed that because Photons where always detected as particles, that one could start from the conclusion that they where particles and build a path from wavefunctions to particles assuming the waves where not detectable. In using a Laser to superposition Xe-135 and Xe-136, one could shoot Neutrinos at a large vat of the Cryogenic substance and determine how many Neutrinos where absorbed from the amount of Gamma Radiation absorbed, and in doing that detect waves, in contradiction to Feynman's assumption. It would also prove that wavefunctions, as waves play a role in Physics. [Preview Abstract] |
Saturday, October 17, 2015 2:12PM - 2:24PM |
K8.00006: Vernier Scan Analysis for Phenix Run 15 p+p Collisions, sqrt{s} = 200 GeV Gregory Ottino In high energy nuclear physics, cross-section measurements are critical to form an understanding of particle production and they require a characterization of absolute integrated luminosity. The technique used by the PHENIX experiment for luminosity calculations is the Vernier Scan or Van Der Meer Scan. The scan consists of sweeping one beam across the other in the vertical and radial directions in the transverse plane, and then fitting the data of event rate vs. position to a 2D Gaussian distribution. The fit is analyzed to extract the overlap profile of the colliding bunches. The extracted widths, along with the number of protons, are used to calculate the luminosity, $\mathcal{L} $. This, in turn, is used to calculate the p+p cross-section available to the minimum bias trigger, $\sigma_{BBC}$. Further analyses provide various correction factors that refine the measurements of rates and positions, improving the initial calculations of $\mathcal{L}$. Final corrected measurement of $\sigma_{BBC}$ is used to calculate integrated luminosity in any of the cross-section measurements with the relevant PHENIX data set. The current data set to be analyzed is from PHENIX Run 15 p+p collisions at $\sqrt{s} = 200$ GeV. [Preview Abstract] |
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