Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session S5: Beam Physics |
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Sponsoring Units: DPB Chair: James Ellison, Illinois Institute of Technology Room: Key 1 |
Monday, April 13, 2015 1:30PM - 1:42PM |
S5.00001: ABSTRACT WITHDRAWN |
Monday, April 13, 2015 1:42PM - 1:54PM |
S5.00002: Beam-Plasma Interaction in Muon Ionization Cooling Lattices James Ellison, Pavel Snopok New computational tools are essential for accurate modeling and simulation of the next generation of muon-based accelerator experiments. There are a number of software packages available to the muon accelerator community that allow detailed simulations with many physics processes accounted for. However, there is also a list of missing physics processes that require implementation or interfacing with other codes. This list is being prioritized, and the most important processes addressed. One of the crucial physics processes specific to muon accelerators that has not yet been implemented in any current simulation code is beam-induced plasma effect in liquid, solid, and gaseous absorbers that are key elements of a cooling channel. We report here on the progress of developing the required simulation tools and applying them to study the properties of plasma and its effects on the beam in muon ionization cooling channels. [Preview Abstract] |
Monday, April 13, 2015 1:54PM - 2:06PM |
S5.00003: ABSTRACT WITHDRAWN |
Monday, April 13, 2015 2:06PM - 2:18PM |
S5.00004: Redetermining CEBAF's Absolute Energy Tong Su With the upgrade of the Jefferson Lab accelerator (CEBAF) from 6 GeV max energy to 12 GeV, all the dipole magnets in the machine were refurbished. Most of them were switched from open c-shaped to closed h-shaped by adding extra iron. With these upgraded magnets, the energy calibration of the accelerator needed to be redetermined. We will show how an extra external dipole, which is run in series with those in the machine, helps us cross check the current in the magnets as well as precisely map out the integral field for any machine setting. Using knowledge of the relative performance of the dipoles as well as the bend angle into the Hall, has allowed us to already determine a 4th pass 7 GeV beam to better than 7 MeV. In the future, we will use g-2 spin precession as a second independent energy determination. This work is supported by Kent State University, NSF Grant PHY-1405814, and DOE Contract DE-AC05-06OR23177 (JLab). [Preview Abstract] |
Monday, April 13, 2015 2:18PM - 2:30PM |
S5.00005: ABSTRACT MOVED TO D1.00027 |
Monday, April 13, 2015 2:30PM - 2:42PM |
S5.00006: Direct injection into the IsoDAR Cyclotron using a RFQ Spencer Axani Beginning in the 1970s, the use of Radio Frequency Quadrupoles (RFQs) has been pervasive in linear accelerators in order to accelerate, bunch, and separate ion species. Current research suggests this may be an ideal way to inject a low energy H2$+$ beam axially into a cyclotron. The IsoDAR (Isotope Decay At Rest) experiment aims to implement this injection system in order to achieve higher Low Energy Beam Transport (LEBT) efficiencies and ultimately construct a novel compact neutrino factory to test the hypothesis of sterile neutrinos. This talk will focus on the research and development needed to implement a RFQ into the IsoDAR experiment. [Preview Abstract] |
(Author Not Attending)
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S5.00007: Experimental Results from a Resonant Dielectric Laser Accelerator Rodney Yoder, Joshua McNeur, Esin Sozer, Gil Travish, Kiran Shankar Hazra, Brian Matthews, Joel England, Edgar Peralta, Ziran Wu Laser-powered accelerators have the potential to operate with very large accelerating gradients ($\sim$ GV/m) and represent a path toward extremely compact colliders and accelerator technology. Optical-scale laser-powered devices based on field-shaping structures (known as dielectric laser accelerators, or DLAs) have been described and demonstrated recently. Here we report on the first experimental results from the Micro-Accelerator Platform (MAP), a DLA based on a slab-symmetric resonant optical-scale structure. As a resonant (rather than near-field) device, the MAP is distinct from other DLAs. Its cavity resonance enhances its accelerating field relative to the incoming laser fields, which are coupled efficiently through a diffractive optic on the upper face of the device. The MAP demonstrated modest accelerating gradients in recent experiments, in which it was powered by a Ti:Sapphire laser well below its breakdown limit. More detailed results and some implications for future developments will be discussed. [Preview Abstract] |
Monday, April 13, 2015 2:54PM - 3:06PM |
S5.00008: Modeling Photoemission of Spin-Polarized Electrons from NEA GaAs Photocathodes Oksana Chubenko, Andrei Afanasev At present, photoemission from strained GaAs activated to negative electron affinity (NEA) is a main source of polarized electrons for modern nuclear-physics and particle-physics facilities. Future experiments at advanced electron colliders will require high-current polarized electron beams, which could provide high polarization and luminosity. This sets new requirements for photocathodes in terms of high quantum efficiency (QE) ($\gg$1\%) and spin polarization ($\sim$85\%). Detailed simulation and modeling of physics processes in photocathodes is important for optimization of their design in order to achieve high QE and reduce depolarization mechanisms. The purpose of the present work was to develop a semi-phenomenological model, which could predict photoemission and electron spin polarization from NEA GaAs photocathodes. Effect of the presence of nanostructures was also studied. Simulation results were compared to the experimental results obtained by the polarized electron source group at Thomas Jefferson National Accelerator Facility. [Preview Abstract] |
Monday, April 13, 2015 3:06PM - 3:18PM |
S5.00009: High-Flux Neutron Generator Facility for Geochronology and Nuclear Physics Research Cory Waltz A facility based on a next-generation, high-flux D-D neutron generator (HFNG) is being commissioned at UC Berkeley. The generator is designed to produce monoenergetic 2.45 MeV neutrons at outputs exceeding 10$^{\mathrm{11}}$ n/s. The HFNG is designed around two RF-driven multi-cusp ion sources that straddle a titanium-coated copper target. D$+$ ions, accelerated up to 150 keV from the ion sources, self-load the target and drive neutron generation through the d(d,n)$^{\mathrm{3}}$He fusion reaction. A well-integrated cooling system is capable of handling beam power reaching 120 kW impinging on the target. The unique design of the HFNG target permits experimental samples to be placed inside the target volume, allowing the samples to receive the highest neutron flux (10$^{\mathrm{11}}$ cm$^{\mathrm{-2}}$s$^{\mathrm{-1}})$ possible from the generator. In addition, external beams of neutrons will be available simultaneously, ranging from thermal to 2.45 MeV. Achieving the highest neutron yields required carefully designed schemes to mitigate back-streaming of high energy electrons liberated from the cathode target by deuteron bombardment. The proposed science program is focused on pioneering advances in the $^{\mathrm{40}}$Ar/$^{\mathrm{39}}$Ar dating technique for geochronology, new nuclear data measurements, basic nuclear science, and education. An end goal is to become a user facility for researchers. This work is supported by NSF Grant No. EAR-0960138, U.S. DOE LBNL Contract No. DE-AC02-05CH11231, U.S. DOE LLNL Contract No. DE-AC52-07NA27344, and UC Office of the President Award 12-LR-238745. [Preview Abstract] |
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