Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session X13: Particle Accelerators and Technologies |
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Sponsoring Units: DPB Chair: Vladimir Shiltsev, Fermi National Accelerator Laboratory Room: Sheraton Plaza Court 2 |
Tuesday, April 16, 2019 10:45AM - 10:57AM |
X13.00001: Simulations of Electron Cooling for a Polarized Electron-Ion Collider Design Ilya V Pogorelov, Dan T Abell, David L Bruhwiler, Yuri Eidelman, Michael Keilman, Paul Moeller, Robert Nagler, Stephen D Webb, He Zhang, Yuhong Zhang Relativistic magnetized electron cooling is essential for achieving the ion beam luminosity requirements of proposed electron-ion collider (EIC) designs. Because the cooling system will have to operate in previously untested parameter regimes, accurate calculations of magnetized dynamic friction are required at the design stage. In particular, one has to include all relevant physics that might increase the cooling time, such as space charge forces, field errors and complicated phase space distributions of imperfectly magnetized electron beams. We present simulations relevant to the JLEIC design, performed with the BETACOOL and JSPEC codes, as well as RadiaSoft's Sirepo interface to JLEIC. We also present recent work on a new semi-analytic treatment of momentum transfer from a single magnetized electron to a drifting ion, and its use for calculations of dynamic friction. |
Tuesday, April 16, 2019 10:57AM - 11:09AM |
X13.00002: Recent Developments in Integrable Optics for IOTA Jonathan P Edelen, Dan T Abell, David L Bruhwiler, Nathan M Cook, Christopher Hall, Stephen D Webb, Jeffrey S Eldred, Aleksandr L Romanov, Alexander Valishev The Integrable Optics Test Accelerator (IOTA) currently being commissioned at Fermilab was constructed for studying the concept of nonlinear integrable optics. The use of a special nonlinear magnetic element introduces large tune spread with amplitude while constraining the idealized dynamics by two integrals of motion. The requirement to preserve this integrability is that the intervening optics appear as a linear, symmetrically focusing lens. Effects such as chromaticity, higher-order dispersion, space charge and coupling may disrupt this assumption. At RadiaSoft, we have studied a variety of these effects in IOTA and how they relate to preserving the integrability of the machine. Here we discuss recent results on nonlinear decoherence, symplectic space-charge tracking, and the impact of synchro-betatron coupling on nonlinear optics. |
Tuesday, April 16, 2019 11:09AM - 11:21AM |
X13.00003: Transverse Beam Evolution in a Plasma Wakefield Accelerator with Plasma Density Ramps Robert Ariniello, Christopher E Doss, Keenan Hunt-Stone, Michael Dennis Litos, John Robert Cary A plasma density ramp at the entrance and exit of a plasma-based accelerator can limit the chromatic emittance growth within the accelerator by controlling the focusing of the beam into and out of the plasma. It is challenging, however, to determine an effective plasma density profile. We present an analytic theory to describe the transverse evolution of an electron beam in a longitudinal plasma density profile. We classify the evolution into three distinct regimes: adiabatic, non-adiabatic, and perturbative. We show that analytic solutions can be calculated for beams with arbitrary chromatic content in the adiabatic and perturbative regimes, and for several cases in the non-adiabatic regime. Further, we show how the theory can be used to determine the effect the shape of the ramp has on the chromatic emittance growth in the ramp and the incoming beam parameters required for matching.
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Tuesday, April 16, 2019 11:21AM - 11:33AM |
X13.00004: Unidirectional Focusing Dipole Magnet as a Gamma-Ray Spectrometer in the Intermediate MeV Range Ganesh Tiwari, Rotem Kupfer, Xuejing Jiao, Joseph Shaw, Andrea Hannasch, Erhard Gaul, Michael C Downer, Bjorn Manuel Hegelich We report on the design of a compact electron and positron spectrometer based on tapered NdFeB magnets. Using RADIA and fourth order Runge-Kutta Particle Tracking code, we show that the tapered design forms a gradient-magnetic field component allowing energy dependent focusing of the dispersed charged particles along a chosen detector plane. We address the effect of incident beam divergence on the efficiency and resolution of the detector. We demonstrate a prototype matching the design specifications and discuss the adaptation of the prototype for the detection of gamma-ray in the multi-MeV range. We confirm the energy transfer of gamma-ray to electrons and positrons via Compton Scattering and Pair Production in a low or intermediate Z-converter by using Monte Carlo based FLUKA simulations. We show that for suitable thickness of the converter, the incident gamma-ray energy spectrum directly correlates with the spectrum of electrons and positrons in a constrict acceptance angle. We investigate the effects of divergence on the spectral deconvolution of incident gamma photon. We present the first series of data obtained with this spectrometer at Texas Petawatt Facility. |
Tuesday, April 16, 2019 11:33AM - 11:45AM |
X13.00005: Designing a Lens-Coupled Plastic Scintillator as a Pulsed Beam Diagnostic Christopher Johnson, Sy Stange, Sukesh Aghara, Darren McGlinchey This work presents the design and characterization of a novel detector consisting of a plastic scintillator tile that uses a biconvex lens to couple to an optical fiber. The detector is intended for use as a beam diagnostic for pulsed power sources, specifically Los Alamos National Laboratory’s (LANL) Dual-Axis Radiographic Hydrodynamic Test Facility (DARHT). A series of these detectors is intended to be placed directly in the accelerator’s X-ray beam such that the neutron background may be deconvolved through time of flight calculations. This work outlines the use of the Geant4 Monte Carlo simulation toolkit to model the detector’s response including its light transport to the photomultiplier tube (PMT). These simulations were validated with benchtop calibration experiments. Additionally, scoring optical photons incident on the PMT’s photocathode by wavelength and time in simulation allows the detector to be used for absolute magnitude and timing measurements. |
Tuesday, April 16, 2019 11:45AM - 11:57AM |
X13.00006: IsoDAR: A Cyclotron-Based Neutrino Source with Applications to Medical Isotope Production Loyd Waites The Isotope Decay-At-Rest (IsoDAR) experiment is a short baseline neutrino experiment designed to measure neutrino oscillations by placing a high flux anti-neutrino source near a kiloton scale scintillator detector. A high current proton beam will be used to produce the large number of anti-neutrinos needed. Reaching the design goal of 10 mA of 60 MeV protons on target requires advancements in accelerator technology. This will be achieved using a high intensity H2+ ion source followed by a radio-frequency quadrupole and spiral inflector to axially inject ions into a compact cyclotron. This high current cyclotron could also be applied to producing valuable isotopes in quantities that are beyond the reach of existing technology. We will discuss the results of our latest studies of this injection system. This work is being presented on behalf of the IsoDAR collaboration |
Tuesday, April 16, 2019 11:57AM - 12:09PM |
X13.00007: Laser Positron Accelerator - Novel Applications Aakash Sahai, Alec Thomas, J R Cary, Mark Golkowski, Vijay Harid, Cameron Geddes, Toshiki Tajima A recently uncovered laser positron accelerator [Sahai, PRAB 21, 081301, 2018] for the first time makes possible production of ultra-short hundreds of MeV quasi-monoenergetic pico-Coulomb positron beams using currently available tens of Joule ultrafast CPA laser system. This groundbreaking model shows that acceleration of high-quality positron beam requires systematic understanding of the physics of interaction of laser-driven plasma-wave and laser-driven electromagnetic-shower. It takes advantage of the small source-size of the laser-driven electromagnetic-shower and the large tunable trapping potential of the laser-driven relativistic plasma-wave. While this technique has been verified using large-scale Particle-In-Cell computational modeling, its first experimental verification is still work in progress under the guidance of this model. In this work we explore certain important applications of hundreds of MeV positron beams. Although these applications hold the promise of paving new pathways they require positron beam characteristics which lay out major future challenges for the above model and demand new breakthroughs. These applications however put forth a strong case for positron beam production by ultrafast CPA laser-driven as uncovered by the above novel model. |
Tuesday, April 16, 2019 12:09PM - 12:21PM |
X13.00008: Photon jets from laser-plasma interactions Lance Labun, Scott V Luedtke, Ou Z. Labun, Karl-Ulrich Bamberg, Hartmut Ruhl, B Manuel Hegelich Advances in high-intensity laser technology have suggested new ways to generate high-flux, short-duration beams of high-energy particles. Numerical simulations have shown that laser intensities >1021 W/cm2 incident on opaque plasma targets yield high-energy photon (Eγ>1 MeV) fluxes of 109 up to 1012 per sterradian. When the laser intensity and plasma density are matched such that the laser creates a low-density channel through the target, the photon flux is concentrated into two jet-like regions aligned with the polarization plane. We quantify the collimation of the photon jets by introducing a jet energy observable, which can be straightforwardly measured and offers a quality measure of the photon beam. We use the observable to demonstrate that the jet phenomenon survives and can be enhanced under non-ideal laser and plasma initial conditions. |
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