Paper |
Title |
Other Keywords |
Page |
TUBX01 |
Impedance and radiation generated by a ceramic chamber with RF shields and TiN coating
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impedance, electromagnetic-fields, synchrotron, extraction |
125 |
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- Y. H. Chin, S. Lee, K. Takata, T. Toyama
KEK, Ibaraki
- Y. Shobuda
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
- H. Tsutsui
SHI, Tokyo
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In the RCS (Rapid Cycle Synchrotron) ring of J-PARC, we use ceramic chambers with the interior TiN coating and exterior Cu RF shields in the magnet sections. A new theory has been developed for calculation of impedance in this unusual configuration. When it was applied to a prototype RCS ceramic chamber, the calculation results got good agreement with the measurement results. We also considered the dipole radiation from gaps between Cu shields of the ceramic chamber in the bending magnets. The effects turn out to be rather small thanks to the special configuration of the ceramic chambers. We measured the radiation from a ceramic break with and without RF shields and capacitors in the KEK, PS and found that the RF shields with capacitors considerably suppress the radiation from the ceramic break. We summarize all these studies in this paper.
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TUBX02 |
Collective Transverse Instabilities in the GSI Synchrotrons
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damping, simulation, octupole, impedance |
131 |
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- V. Kornilov, O. Boine-Frankenheim, I. Hofmann
GSI, Darmstadt
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One of the primary challenges for the design of the FAIR synchrotrons at GSI Darmstadt is the high current operation close to the stability limits, with small tolerable beam losses. Collective instabilities are a potential limiting factor for the performance of the rings. We discuss results of experimental and numerical investigations of transverse collective beam behavior in the SIS 18 synchrotron. Also damping mechanisms in the presence of space charge, including the linear Landau damping and decoherence due to nonlinearities are discussed. These are the essential factors to define impedances budgets for the GSI synchrotrons. As a computational tool accounting the beam nonlinear dynamics with impedances and self-consistent space charge, the particle tracking code PATRIC is used.
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WEAX01 |
Resonance trapping due to space charge and synchrotron motion, in theory, simulations, and experiments
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beam-losses, resonance, emittance, synchrotron |
167 |
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- G. Franchetti, I. Hofmann
GSI, Darmstadt
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With the development of high intensity accelerator, the role of space charge effect in a nonlinear lattice gained special attention, as in the FAIR project at GSI, where long term storage of high intensity beams is required. The simultaneous presence of space charge and a nonlinear lattice creates an unprecedented challenge for ring designers as well as a new area of studies in beam physics. We present our understanding of the effect of space charge and chromaticity on the nonlinear beam dynamics of a bunched beam.
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WEAX02 |
Space charge simulation of J-PARC main ring
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injection, resonance, sextupole, emittance |
177 |
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- A. Y. Molodozhentsev, M. Tomizawa
KEK, Ibaraki
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The space charge effect in combination with the intrinsic field nonlinearity like the sextupole nonlinearity, used for the chromaticity correction, could lead to significant particle losses in a high beam intensity proton machine. For J-PARC Main Ring (MR) the total particle losses at the rings collimator should be less than 1% from the expected maximum beam power of 45kW at the injection energy of 3GeV. To keep the particle losses during the injection process within the required limit it is necessary to optimize the beam parameters from the injector (J-PARC RCS), the collimator aperture of the beam-line from RCS to MR and the collimator aperture of MR. Influence of the structure and non-structure high-order resonances for different working points is discussed. The budget of the beam losses for different MR commissioning scenario is presented.
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WEAX03 |
Space charge neutralization and its dynamic effects
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electron, linac, simulation, proton |
187 |
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- R. Duperrier, N. Pichoff, D. Uriot
CEA, Gif-sur-Yvette
- A. BenIsmail
LLR, Palaiseau
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High-power accelerators are being studied for several projects including accelerator driven neutron or neutrino sources. The low energy part of these facilities has to be carefully optimized to match the beam requirements of the higher energy parts. In this low energy part, the space charge self force, induced by a high intensity beam, has to be carefully controlled. This nonlinear force can generate a large and irreversible emittance growth of the beam. To reduce the space charge (SC), neutralization of the beam charge can be done by capturing some particles of the ionised residual gas in the vacuum chamber. This space charge compensation (SCC) regime complicates the beam dynamics study. This contribution aims to modelize the beam behavior in such a regime and to give order of magnitude to the linac designer for the neutralization rise time and the induced emittance growth.
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WEAX04 |
High Intensity Cyclotron Simulations: Towards Quantitative Predictions
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simulation, cyclotron, injection, proton |
202 |
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- A. Adelmann, S. R.A. Adam, M. Humbel, P. A. Schmelzbach
PSI, Villigen
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PSI operates the most powerful cyclotron worldwide to the benefit of a multi-user, cross-disciplinary research facility. The accelerator complex consists of a Cockcroft-Walton pre-injector, a 72-MeV separated sector injector cyclotron and a 590-MeV separated sector Ring Cyclotron. A beam current of 1.9 mA is routinely extracted from the Ring Cyclotron overall absolute losses are below 1·10-3. The facility has a considerable potential for further improvements, an ongoing upgrade project aims at a beam current of 3 mA. The purpose of our multi-scale three-dimensional parallel code and methods development is to make the step from qualitative to quantitative predictions. Their simulation requires the accurate three-dimensional modeling of large and complicated accelerator structures including space charge, beam lines, collimation, and in the future secondary effects. We will show methods, both numerically and computational, that we use presently and give an overview on future directions. Measurements from the cyclotrons and beamlines will be compared with simulations carried out in the frame of the high intensity upgrade program.
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WEAX05 |
Space-Charge Beam Physics Research at the University of Maryland Electron Ring (UMER)*
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quadrupole, dipole, injection, lattice |
218 |
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- S. Bernal, B. L. Beaudoin, D. W. Feldman, R. Feldman, R. B. Fiorito, T. F. Godlove, I. Haber, R. A. Kishek, P. G. O'Shea, C. Papadopoulos, B. Quinn, D. Stratakis, K. Tian, C. Tobin, M. Walter
IREAP, College Park, Maryland
- M. Reiser
University Maryland, College Park, Maryland
- D. F. Sutter
HENP, SW Washington
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The University of Maryland electron ring (UMER) is a low-energy, high current recirculator for beam physics research with relevance to any applications that rely on intense beams of high quality. We review the space-charge physics issues, experimental and computational investigations, which are currently being conducted at the UMER facility. The physics issues cover a broad range, but we focus on transverse beam dynamics: halo formation, strongly asymmetric beams, Montague resonances, equipartitioning, etc. Furthermore, we report on recent developments in experiments, simulations, and improved diagnostics for space-charge dominated beams.
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WEAX06 |
Measurements and Synergia simulations of emittance dilution at the Fermilab Booster.
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simulation, resonance, injection, booster |
236 |
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WEBX02 |
Observation of Emittance Growth at the injection in the KEK PS Main Ring
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injection, emittance, proton, simulation |
250 |
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- S. Igarashi, T. Miura, E. Nakamura, Y. Shimosaki, M. J. Shirakata, K. Takayama, T. Toyama
KEK, Ibaraki
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We have been studying the emittance growth and beam loss mechanism during the injection period of the 12 GeV main ring of the KEK proton synchrotron to achieve higher intensity. The typical beam loss is about 30 % during the injection period of 500 milliseconds for the high intensity operation. Measurement of the transverse beam profiles using flying wires has revealed a characteristic temporal change of the beam profile within a few milliseconds after the injection. Horizontal emittance growth was observed when the horizontal tune was close to the integer. The effect was more enhanced for higher beam intensity and could not be explained with the injection mismatch. A resonance created by the space charge field was the cause of the emittance growth. A multiparticle tracking simulation program, ACCSIM, taking account of space charge effects has successfully reproduced the beam profiles.
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WEBX05 |
Scaling laws for space charge resonances
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emittance, resonance, focusing, simulation |
268 |
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- I. Hofmann, G. Franchetti
GSI, Darmstadt
- S.-Y. Lee
IUCF, Bloomington, Indiana
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Space charge can be the driving term of nonlinear resonances, like the resonant emittance exchange 2Qx-2Qy=0 ("Montague resonance", in linacs and high-intensity rings), or the fourth-order structure resonance 4Qx=n (high-intensity rings, FFAG's). In this study we present scaling laws to describe the dependence of the expected emittance growth effect on the initial emittances, the tune shift and/or the crossing rate through the resonance.
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WEBX06 |
Analysis of emittance growth in the Fermilab Booster
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emittance, quadrupole, injection, resonance |
271 |
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THAW03 |
RF Barrier Cavity Option for the SNS Ring Beam Power Upgrade
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electron, proton, injection, target |
298 |
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- J. A. Holmes, S. M. Cousineau, V. V. Danilov, A. P. Shishlo
ORNL, Oak Ridge, Tennessee
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RF barrier cavities present an attractive option for facilitating the path to higher beam intensity in the SNS power upgrade. Barrier cavities lead to flat longitudinal current densities, thus minimizing bunch factor effects. In addition to allowing more beam to be injected in this fashion, flat current profiles may lead to increased e-p instability thresholds due to reduced multipacting during the trailing stage of the bunch. Finally, it is possible to inject self-consistent beam distributions into barrier buckets, thus providing the additional advantages of uniform transverse beam density (good for meeting target constraints) and little or no halo (good for low losses). Simulations addressing all these issues will be presented and discussed.
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THBW01 |
Code benchmarking on induce space charge particle trapping
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emittance, resonance, synchrotron, sextupole |
344 |
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FRAP02 |
Summary of Working Gropu B
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simulation, resonance, beam-losses, linac |
363 |
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- S. M. Cousineau
ORNL, Oak Ridge, Tennessee
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