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Stoltz, P.

Paper Title Page
TUXAB03 Self-consistent 3D Modeling of Electron Cloud Dynamics and Beam Response 764
  • M. A. Furman, C. M. Celata, M. Kireeff Covo, K. G. Sonnad, J.-L. Vay, M. Venturini
    LBNL, Berkeley, California
  • R. H. Cohen, A. Friedman, D. P. Grote, A. W. Molvik
    LLNL, Livermore, California
  • P. Stoltz
    Tech-X, Boulder, Colorado
  Funding: Work supported by the U. S. DOE under Contracts DE-AC02-05CH11231 and W-7405-Eng-48, and by the US-LHC Accelerator Research Project (LARP).

We present recent advances in the modeling of beam-electron-cloud dynamics, including surface effects such as secondary electron emission, gas desorption, etc, and volumetric effects such as ionization of residual gas and charge-exchange reactions. Simulations for the HCX facility with the code WARP/POSINST will be described and their validity demonstrated by benchmarks against measurements. The code models a wide range of physical processes and uses a number of novel techniques, including a large-timestep electron mover that smoothly interpolates between direct orbit calculation and guiding-center drift equations, and a new computational technique, based on a Lorentz transformation to a moving frame, that allows the cost of a fully 3D simulation to be reduced to that of a quasi-static approximation.

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TUOAAB01 Self-Consistent Simulations of Multipacting in Superconducting Radio Frequencies 769
  • C. Nieter, P. J. Mullowney, S. Ovtchinnikov, D. S. Smithe, P. Stoltz
    Tech-X, Boulder, Colorado
  Multipacting continues to be an important issue in Superconducting Radio Frequency (SRF) cavities, particularly near waveguide couplers. Most modern simulations of multipacting are not self-consistent, using the fields from a purely electromagnetic simulation to drive the motion of multipacting electrons. This approach works well for the onset on multipacting but as the electron density increases in the cavity it can have an effect on the cavity mode. Recently VORPAL* has demonstrated its ability to mode the electrodynamics of SRF cavities using finite difference time domain (FDTD) algorithms coupled with the Dey-Mittra** method for modeling conformal boundaries. The FDTD approach allows us to easily incorporate multipacting electrons as PIC particles in the simulations. To allow multipacting simulations to be done with EM-PIC we have been developing particle boundaries for the cut-cells. Recently we have added particle removal boundaries at the particle sinks which will correct the unphysical build up of image charge at the boundaries. Work has begun on incorporating secondary electron emission into these boundaries so VORPAL can model multipacting trajectories self-consistently.

* C. Nieter, J. R. Cary, J. Comp. Phys. 196 (2004) 448.** S. Dey, R. Mittra, IEEE Microwave and Guided Wave Letters 7 (1997) 273.

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WEPMN089 A General Model of High Gradient Limits 2236
  • J. Norem
    ANL, Argonne, Illinois
  • D. Huang
    IIT, Chicago, Illinois
  • P. Stoltz, S. A. Veitzer
    Tech-X, Boulder, Colorado
  Funding: Supported by the USDOE / Office of High Energy Physics

Recent experimental work done to develop high gradient, low frequency cavities for muon cooling, has led to a model of rf breakdown and high gradient limits in warm structures. We have recently been extending this model to try to explain some superconducing rf quench mechanisms, as well as DC and dielectric breakdown. The model assumes that the dominant mechanisms in warm metal systems are fractures caused by the the electric tensile stress, and surface micro-topography that is strongly determined by the the cavity design and history*. We describe how these processes can determine all measurable parameters in warm systems. With superconducting systems, these mechanisms also apply, however field emission, impurities and temperature produce a somewhat different picture of quenching and pulsed power processing. We describe the model and some recent extensions and improvements in some detail and a variety of results accelerators and other applications.

* Hassanein et. al. Phys. Rev. STAB, 9, 062001

WEOCKI03 Status of the R&D Towards Electron Cooling of RHIC 1938
  • I. Ben-Zvi, J. Alduino, D. S. Barton, D. Beavis, M. Blaskiewicz, J. M. Brennan, A. Burrill, R. Calaga, P. Cameron, X. Chang, K. A. Drees, A. V. Fedotov, W. Fischer, G. Ganetis, D. M. Gassner, J. G. Grimes, H. Hahn, L. R. Hammons, A. Hershcovitch, H.-C. Hseuh, D. Kayran, J. Kewisch, R. F. Lambiase, D. L. Lederle, V. Litvinenko, C. Longo, W. W. MacKay, G. J. Mahler, G. T. McIntyre, W. Meng, B. Oerter, C. Pai, G. Parzen, D. Pate, D. Phillips, S. R. Plate, E. Pozdeyev, T. Rao, J. Reich, T. Roser, A. G. Ruggiero, T. Russo, C. Schultheiss, Z. Segalov, J. Smedley, K. Smith, T. Tallerico, S. Tepikian, R. Than, R. J. Todd, D. Trbojevic, J. E. Tuozzolo, P. Wanderer, G. Wang, D. Weiss, Q. Wu, K. Yip, A. Zaltsman
    BNL, Upton, Long Island, New York
  • D. T. Abell, G. I. Bell, D. L. Bruhwiler, R. Busby, J. R. Cary, D. A. Dimitrov, P. Messmer, V. H. Ranjbar, D. S. Smithe, A. V. Sobol, P. Stoltz
    Tech-X, Boulder, Colorado
  • A. V. Aleksandrov, D. L. Douglas, Y. W. Kang
    ORNL, Oak Ridge, Tennessee
  • H. Bluem, M. D. Cole, A. J. Favale, D. Holmes, J. Rathke, T. Schultheiss, J. J. Sredniawski, A. M.M. Todd
    AES, Princeton, New Jersey
  • A. V. Burov, S. Nagaitsev, L. R. Prost
    Fermilab, Batavia, Illinois
  • Y. S. Derbenev, P. Kneisel, J. Mammosser, H. L. Phillips, J. P. Preble, C. E. Reece, R. A. Rimmer, J. Saunders, M. Stirbet, H. Wang
    Jefferson Lab, Newport News, Virginia
  • V. V. Parkhomchuk, V. B. Reva
    BINP SB RAS, Novosibirsk
  • A. O. Sidorin, A. V. Smirnov
    JINR, Dubna, Moscow Region
  Funding: Work done under the auspices of the US DOE with support from the US DOD.

The physics interest in a luminosity upgrade of RHIC requires the development of a cooling-frontier facility. Detailed cooling calculations have been made to determine the efficacy of electron cooling of the stored RHIC beams. This has been followed by beam dynamics simulations to establish the feasibility of creating the necessary electron beam. Electron cooling of RHIC at collisions requires electron beam energy up to about 54 MeV at an average current of between 50 to 100 mA and a particularly bright electron beam. The accelerator chosen to generate this electron beam is a superconducting Energy Recovery Linac (ERL) with a superconducting RF gun with a laser-photocathode. An intensive experimental R&D program engages the various elements of the accelerator: Photocathodes of novel design, superconducting RF electron gun of a particularly high current and low emittance, a very high-current ERL cavity and a demonstration ERL using these components.

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THPAS008 Simulation of the Dynamics of Microwave Transmission Through an Electron Cloud 3525
  • K. G. Sonnad, M. A. Furman
    LBNL, Berkeley, California
  • J. R. Cary
    CIPS, Boulder, Colorado
  • P. Stoltz, S. A. Veitzer
    Tech-X, Boulder, Colorado
  Funding: Work supported by the U. S. DOE under Contract no. DE-AC02-05CH11231

Simulation studies are under way to analyze the dynamics of microwave transmission through a beam channel containing electron clouds. Such an interaction is expected to produce a shift in phase accompanied by attenuation in the amplitude of the microwave radiation. Experimental observation of these phenomena would lead to a useful diagnosis tool for electron clouds. This technique has already been studied* at the CERN SPS. Similar experiments are being proposed at the PEP-II LER at SLAC as well as the Fermilab MI. In this study, simulation results will be presented for a number of cases including those representative of the above mentioned experiments. The code VORPAL is being utilized to perform electromagnetic particle-in-cell (PIC) calculations. The results are expected to provide guidance to the above mentioned experiments as well as lead to a better understanding of the problem.

* T. Kroyer, F. Caspers, E. Mahner , pg 2212 Proc. PAC 2005, Knoxville, TN

THPAS019 A Beam Dynamics Application Based on the Common Component Architecture 3552
  • D. R. Dechow, D. T. Abell, P. Stoltz
    Tech-X, Boulder, Colorado
  • J. F. Amundson
    Fermilab, Batavia, Illinois
  • L. Curfman McInnes, B. Norris
    ANL, Argonne, Illinois
  Funding: Department of Engergy, Office of Advanced Scientific Computing Research, SBIR grant: DE-FG02-06ER84520

A component-based beam dynamics application for modeling collective effects in particle accelerators has been developed. The Common Component Architecture (CCA) software infrastructure was used to compose a new Python-steered accelerator simulation from a set of services provided by two separate beam dynamics packages (Synergia and MaryLie/Impact) and two high-performance computer science packages (PETSc and FFTW). The development of the proof-of-concept application was accomplished via the following tasks:

  1. addressing multilanguage interoperability in the MaryLie/Impact code with Babel;
  2. creating components by making the selected software objects adhere to the Common Component Architecture protocol;
  3. assemblying the components with a newly developed, Component Builder gui; and
  4. characterizing the performance of the space charge (Poisson) solver that was originally used in Synergia 1.0 versus the PETSc-based space charge solver that has been developed for Synergia2.
The resulting beam dynamics application will allow the Synergia2 framework to evolve simultaneously with the modeling and simulation requirements of the International Linear Collider.