| Paper |
Title |
Page |
| THAW01 |
New simulation capabilities of electron clouds in ion beams with large tune depression
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279 |
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- J.-L. Vay, M. A. Furman, P. A. Seidl
LBNL, Berkeley, California
- R. H. Cohen, A. Friedman, D. P. Grote, M. Kireeff Covo, A. W. Molvik
LLNL, Livermore, California
- P. Stoltz, S. A. Veitzer
Tech-X, Boulder, Colorado
- J. Verboncoeur
UCB, Berkeley, California
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We have developed a new, comprehensive set of simulation tools aimed at modeling the interaction of intense ion beams and electron clouds (e-clouds). The set contains the 3-D accelerator PIC code WARP and the 2-D “slice” e-cloud code POSINST [M. Furman, this workshop], as well as a merger of the two, augmented by new modules for impact ionization and neutral gas generation. The new capability runs on workstations or parallel supercomputers and contains advanced features such as mesh refinement, disparate adaptive time stepping, and a new “drift-Lorentz” particle mover for tracking charged particles in magnetic fields using large time steps. It is being applied to the modeling of ion beams (1 MeV, 180 mA, K+) for heavy ion inertial fusion and warm dense matter studies, as they interact with electron clouds in the High-Current Experiment (HCX) [experimental results discussed by A. Molvik, this workshop]. We will describe the capabilities and simulation results with detailed comparisons against the HCX experiment, as well as their application (in a different regime) to the modeling of e-clouds in the Large Hadron Collider (LHC).
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| THAW02 |
New experimental measurements of electron clouds in ion beams with large tune depression*
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288 |
| |
- A. W. Molvik, R. H. Cohen, A. Friedman, M. Kireeff Covo
LLNL, Livermore, California
- F. M. Bieniosek, P. A. Seidl, J.-L. Vay
LBNL, Berkeley, California
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We study electron clouds in high perveance beams (K = 8E-4) with a large tune depression of 0.2 (defined as the ratio of a single particle oscillation response to the applied focusing fields, with and without space charge). These 1 MeV, 180 mA, K+ beams have a beam potential of +2 kV when electron clouds are minimized. Simulation results are discussed in a companion paper [J-L. Vay, this Conference]. We have developed the first diagnostics that quantitatively measure the accumulation of electrons in a beam [M. Kireeff Covo, et al., to be submitted to Phys. Rev. Lett.]. This, together with measurements of electron sources, will enable the electron particle balance to be measured, and electron-trapping efficiencies determined. We measure and simulate ~10 MHz electron oscillations in the last quadrupole magnet when we flood the beam with electrons from an end wall. Experiments where the heavy-ion beam is transported with solenoid magnetic fields, rather than with quadrupole magnetic or electrostatic fields, are being initiated. We will discuss the initial results using electrode sets (in the middle and at the ends of magnets) to either expel or to trap electrons within the magnets.
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| THAW03 |
RF Barrier Cavity Option for the SNS Ring Beam Power Upgrade
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298 |
| |
- 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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| THAW04 |
Experimental Characterization of the “1st Pulse” e-p Instability at the LANL PSR
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311 |
| |
- R. J. Macek, A. A. Browman, D. H. Fitzgerald, R. C. McCrady, T. Spickermann, J. Zaugg
LANL, Los Alamos, New Mexico
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A puzzling aspect of the e-p instability at PSR is the so called “1st Pulse” instability phenomenon. It shows up on the first beam pulse after a period (10 to 30 minutes or more) of beam off time. This pulse has a significantly lower threshold than subsequent beam pulses that follow with the standard time separation. While the standard PSR operation for Lujan Center operation is unaffected by this phenomenon, it does interfere with some high intensity, single pulse experiments using PSR beam. We will summarize the present experimental data characterizing this phenomenon as compared with the typical e-p instability observed at higher repetition rates at PSR and discuss some possible explanations.
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| THAW05 |
Electron Cloud Investigations in the Fermilab Main Injector
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0 |
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- R. M. Zwaska, W. Chou, I. Kourbanis, A. Marchionni, V. D. Shiltsev, X. Zhang
Fermilab, Batavia, Illinois
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The Fermilab Main Injector currently accelerates 300 kW of 120 GeV protons for antiproton and neutrino production. We report on searches for the formation of an electron cloud within the Main Injector, and possible associated proton beam instabilities. Current capabilities and instrumentation upgrades will be discussed. These studies are performed with the anticipation that future plans could lead to a fourfold increase of the proton charge in the Main Injector.
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| THAW06 |
Electron cloud effect in J-PARC
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0 |
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We discuss electron cloud instability in J-PARC proton rings. Instabilities in both of bunched and coasting beam are treated.
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| THAW07 |
Transverse electron-antiproton instability in the Recycler Ring
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334 |
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- A. V. Burov
Fermilab, Batavia, Illinois
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Lifetime degradation of electron-cooled ions was observed at several electron coolers. In the Recycler, both the lifetime drop and emittance growth of the e-cooled pbars are seen. A possible reason for that can be a coherent interaction between the electron and antiproton beams. A theoretical model of this instability is presented, and a practical recommendation for its suppression is explained and discussed.
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