Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session Y14: Particle Accelerators and Applied Plasma Physics |
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Sponsoring Units: DPB DPF Chair: Michiko Minty, BNL Room: A226 |
Tuesday, April 17, 2018 1:30PM - 1:42PM |
Y14.00001: Crab cavity requirements for the Jefferson Lab electron-ion collider Salvador Sosa, Vasiliy Morozov, Subashini de Silva, Fanglei Lin, Jean Delayen An electron-ion collider (EIC) has been agreed as the next step in the understanding of QCD. An EIC is being designed at Jefferson Lab, it considers the CEBAF 12 GeV as a full energy electron injector and envisions the construction of an ion facility and an electron ring. JLEIC detector is based on full acceptance. For this, a large beam crossing angle of 50 mrad is required, which in turn reduces the luminosity by an order of magnitude. JLEIC has a high luminosity requirement of 10$^{34}$ cm$^{-2}$s$^{-1}$, thus a need for compensation. A local crab scheme can be used to compensate for geometric luminosity loss: superconducting radiofrequency crab cavities are placed at both sides of the interaction region. The upstream cavity gives each bunch a longitudinally dependent transverse kick, in such a way as to restore a head-on collision at the interaction point. The downstream cavity cancels the initial transverse kick, thus avoiding synchro-betatron coupling anywhere else along the ring. Based on beam dynamic studies and crab cavity designs, we present requirements on the crab cavity scheme for JLEIC such as voltage, tolerances on multipoles and damping requirements of higher order modes. We use a complete model of both electron and ion rings for particle tracking. [Preview Abstract] |
Tuesday, April 17, 2018 1:42PM - 1:54PM |
Y14.00002: On FCC-hh Momentum Collimation System Aakaash Narayanan The Future Circular Collider (FCC) is a proposed next-generation high-energy accelerator to be built at CERN, aiming at a 100 TeV CoM collision energy of protons, and studies of its design and feasibility are impetuously underway. One such important study is of its collimation systems, comprising of betatron collimation and momentum collimation. Here we look at the momentum collimation in a warm, straight-section (WSS). For the bunch length of 8 cm, and an RF of 400 MHz and 32 MV, the bucket height is about 9 GeV, or a maximum $\frac{dE}{E}$ of about $2 \times 10^{−4}$. But various loss mechanisms can send the particles way outside the bucket, so the intention is to catch particles that are even ten times the bucket height. Within WSS, the system consists of primary, secondary, and perhaps tertiary collimators. The impacts of various parameters, such as their placing, shape, orientation, and materials, are studied, keeping in mind to also optimize the phase advance of the particles from one collimator to the next. We also look at optimizing the optics of the FCC ring in order to facilitate momentum collimation. The study is done first for the traversal of the bunch in the WSS alone, then for one-turn around the full of FCC, and subsequently for very many turns around the ring. [Preview Abstract] |
Tuesday, April 17, 2018 1:54PM - 2:06PM |
Y14.00003: The upgrade of the CMS forward pixel detector for the HL-LHC Abraham Mathew Koshy, Joshua Leeman, Andreas Jung The Large Hadron Collider (LHC) at CERN is a unique place in the world for research in particle physics, most recently made famous by confirming the existence of the Higgs Boson in 2012. The high-luminosity upgrade of the LHC (HL-LHC), scheduled for 2023, will generate a higher instantaneous luminosity than ever before. The HL-LHC poses an extreme environment to the innermost CMS detector region and, hence CMS currently designs a lightweight silicon pixel detector that can withstand the higher particle flux. Measurements of thermal conductivities of various materials are carried out and are used as an input to thermal simulations of heat dissipation of possible low-mass detector designs. The results of these simulations are compared with data of mock-up detector prototypes accumulated employing a CO2 cold box setup emulating the CMS detector cooling scheme. [Preview Abstract] |
Tuesday, April 17, 2018 2:06PM - 2:18PM |
Y14.00004: Modeling Magnetic Fields using Helical Solutions to Maxwell's Equations Brian Pollack, Ryan Pellico, Michael Schmitt The current generation of HEP experiments require precise knowledge of the magnetic fields that permeate detector hardware. After a solenoid is constructed, the field produced will always differ from simulations due to unavoidable real-world limitations and tolerances. We explore a novel method in which one can accurately and precisely model a solenoidal field from a sparse series of field measurements, using a series solution to Maxwell's Equations. In order to model the small but non-negligible axial asymmetry due to the winding of a solenoid, we use a helical coordinate system in which to solve said equations. Using this method, one can obtain a full three dimensional vector field that is reliable to over 4 orders of magnitude, and guarantees a physically sound result that cannot be obtained through interpolation methods. [Preview Abstract] |
Tuesday, April 17, 2018 2:18PM - 2:30PM |
Y14.00005: Dynamical bunching and density peaks in expanding Coulomb clouds Brandon Zerbe, Xukun Xiang, Chong-Yu Ruan, Steve Lund, Phil Duxbury Expansion dynamics of single-species, non-neutral clouds, such as electron bunches used in ultrafast electron microscopy, show novel behavior due to high acceleration of particles in the cloud interior. This often leads to electron bunching and dynamical formation of a density shock in the outer regions of the bunch. We develop analytic fluid models to capture these effects, and the analytic predictions are validated by PIC and N-particle simulations. In the space-charge dominated regime, two and three dimensional systems with Gaussian initial densities show bunching and a strong shock response, while one dimensional systems do not. [Preview Abstract] |
Tuesday, April 17, 2018 2:30PM - 2:42PM |
Y14.00006: First direct observation of runaway electron-driven whistler waves in tokamaks D.A. Spong, W.W. Heidbrink, C. Paz-Soldan, X.D. Du, K.E. Thome, M.A. Van Zeeland, C. Collins, A. Lvovskiy, R.A. Moyer, D.P. Brennan, C. Liu, E.F. Jaeger, C. Lau Whistlers are electromagnetic waves destabilized by energetic electrons and are observed in natural plasmas, such as planetary ionospheres. Recent experiments on the DIII-D tokamak at low density demonstrate the first direct observation of whistlers in tokamaks, with 100 to 200 MHz waves excited by runaway electrons (REs) in the multi-MeV range. The whistlers are correlated with RE intensity and the frequency scaling is consistent with a whistler dispersion relation. Fluctuations occur in discrete frequency bands, and not a continuum as would be expected from plane wave analysis. An RF absorption model has been applied, indicating a set of discrete cavity modes are formed as a result of the bounded, periodic nature of the plasma. The instabilities are stabilized with increasing magnetic field, as expected from the anomalous Doppler resonance. Whistler amplitudes show intermittent predator-prey cycles, which can be interpreted as wave-induced scattering of REs. These features have connections to ionospheric plasmas and open possibilities for active control of tokamak REs. [Preview Abstract] |
Tuesday, April 17, 2018 2:42PM - 2:54PM |
Y14.00007: Abstract Withdrawn
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Tuesday, April 17, 2018 2:54PM - 3:06PM |
Y14.00008: First Ever Ionization Cooling Demonstration in MICE Varrick Suezaki, Vittorio Palladino The Muon Ionization Cooling Experiment (MICE) at RAL has studied the ionization cooling of muons. Several million individual particle tracks have been recorded passing through a series of focusing magnets in a number of different configurations and a liquid hydrogen or lithium hydride absorber. Measurement of the tracks upstream and downstream of the absorber has shown the expected effects of the 4D emittance reduction. This invited talk presents and discusses these results, and projects the future of ionization cooling. [Preview Abstract] |
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