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Title: Beam Breakup Effects in Dielectric Based Accelerators

Abstract

The dynamics of the beam in structure-based wakefield accelerators leads to beam stability issues not ordinarily found in other machines. In particular, the high current drive beam in an efficient wakefield accelerator loses a large fraction of its energy in the decelerator structure, resulting in physical emittance growth, increased energy spread, and the possibility of head-tail instability for an off axis beam, all of which can lead to severe reduction of beam intensity. Beam breakup (BBU) effects resulting from parasitic wakefields provide a potentially serious limitation to the performance of dielectric structure based wakefield accelerators as well. We report on experimental and numerical investigation of BBU and its mitigation. The experimental program focuses on BBU measurements at the AWA facility in a number of high gradient and high transformer ratio wakefield devices. New pickup-based beam diagnostics will provide methods for studying parasitic wakefields that are currently unavailable. The numerical part of this research is based on a particle-Green's function beam breakup code we are developing that allows rapid, efficient simulation of beam breakup effects in advanced linear accelerators. The goal of this work is to be able to compare the results of detailed experimental measurements with the accurate numerical resultsmore » and to design an external FODO channel for the control of the beam in the presence of strong transverse wakefields.« less

Authors:
;  [1];  [1];  [2];  [3];  [4]; ;  [5]
  1. Euclid Techlabs LLC, Solon, OH 44139 (United States)
  2. (United States)
  3. Dynamics Software, Helsinki (Finland)
  4. Electrotechnical University Eltech 'LETI', St. Petersburg (Russian Federation)
  5. Argonne National Laboratory, IL (United States)
Publication Date:
OSTI Identifier:
21255255
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1086; Journal Issue: 1; Conference: 13. advanced accelerator concepts workshop, Santa Cruz, CA (United States), 27 Jul - 2 Aug 2008; Other Information: DOI: 10.1063/1.3080941; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DIELECTRIC MATERIALS; GREEN FUNCTION; INSTABILITY; MITIGATION; PERFORMANCE; SIMULATION; SPACE CHARGE; STABILITY; TRANSFORMERS; WAKEFIELD ACCELERATORS

Citation Formats

Schoessow, P., Kanareykin, A., Jing, C., Argonne National Laboratory, IL, Kustov, A., Altmark, A., Power, J. G., and Gai, W. Beam Breakup Effects in Dielectric Based Accelerators. United States: N. p., 2009. Web. doi:10.1063/1.3080941.
Schoessow, P., Kanareykin, A., Jing, C., Argonne National Laboratory, IL, Kustov, A., Altmark, A., Power, J. G., & Gai, W. Beam Breakup Effects in Dielectric Based Accelerators. United States. doi:10.1063/1.3080941.
Schoessow, P., Kanareykin, A., Jing, C., Argonne National Laboratory, IL, Kustov, A., Altmark, A., Power, J. G., and Gai, W. 2009. "Beam Breakup Effects in Dielectric Based Accelerators". United States. doi:10.1063/1.3080941.
@article{osti_21255255,
title = {Beam Breakup Effects in Dielectric Based Accelerators},
author = {Schoessow, P. and Kanareykin, A. and Jing, C. and Argonne National Laboratory, IL and Kustov, A. and Altmark, A. and Power, J. G. and Gai, W.},
abstractNote = {The dynamics of the beam in structure-based wakefield accelerators leads to beam stability issues not ordinarily found in other machines. In particular, the high current drive beam in an efficient wakefield accelerator loses a large fraction of its energy in the decelerator structure, resulting in physical emittance growth, increased energy spread, and the possibility of head-tail instability for an off axis beam, all of which can lead to severe reduction of beam intensity. Beam breakup (BBU) effects resulting from parasitic wakefields provide a potentially serious limitation to the performance of dielectric structure based wakefield accelerators as well. We report on experimental and numerical investigation of BBU and its mitigation. The experimental program focuses on BBU measurements at the AWA facility in a number of high gradient and high transformer ratio wakefield devices. New pickup-based beam diagnostics will provide methods for studying parasitic wakefields that are currently unavailable. The numerical part of this research is based on a particle-Green's function beam breakup code we are developing that allows rapid, efficient simulation of beam breakup effects in advanced linear accelerators. The goal of this work is to be able to compare the results of detailed experimental measurements with the accurate numerical results and to design an external FODO channel for the control of the beam in the presence of strong transverse wakefields.},
doi = {10.1063/1.3080941},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1086,
place = {United States},
year = 2009,
month = 1
}
  • Structure mode frequency spreads are shown to have a rather different influence on beam breakup growths than betatron frequency spreads. The present analytic and numerical studies show that a finite spread in the breakup mode frequency leads to an algebraic decay of the beam breakup instabilities even if the quality factor /ital Q//r arrow/infinity. Effects of stagger tuning are examined.
  • An analytic formalism of cumulative beam breakup in linear accelerators is developed. This formalism is applied to both low-velocity ion accelerators and high-energy electron accelerators. It includes arbitrary velocity, acceleration, focusing, initial conditions, beam-cavity resonances, finite bunch length, and arbitrary charge distribution within the bunches, and variable cavity geometry and spacing along the accelerator. For both direct-current beams and beams comprised of {delta}-function bunches, both the steady-state and transient displacements of the beam are calculated, and scaling laws are determined for the transient beam breakup. The steady-state transverse displacement of particles between bunches is also calculated since, if allowed tomore » impinge on the accelerating structures, these particles could cause activation over long periods of continuous-wave operation. The formalism is then applied to high-current ion accelerators by studying the effects of finite bunch length and arbitrary charge distribution within the bunches. The role of focusing in controlling cumulative beam breakup is quantified in each of these cases. Additionally, the effects of random initial conditions and a distribution of deflecting-mode frequencies in the cavities are also quantified.« less
  • An analytical formalism for the solution of cumulative beam breakup in linear accelerators with arbitrary time dependence of beam current is presented, and a closed-form expression for the time and position dependence of the transverse displacement is obtained. It is applied to the behavior of single bunches and to the steady state and transient behavior of dc beams and beams composed of point-like and finite length bunches. This formalism is also applied to the problem of cumulative beam breakup in the presence of random displacement of cavities and focusing elements, and a general solution is presented.
  • A particle-Green's function beam dynamics code (BBU-3000) to study beam breakup effects is incorporated into a parallel computing framework based on the Boinc software environment, and supports both task farming on a heterogeneous cluster and local grid computing. User access to the platform is through a web browser.
  • The temporal and spatial evolution of the cumulative beam breakup instability (BBU) is analyzed numerically using a continuum model. It is found that neither phase mixing nor linear transverse focusing is sufficient to render BBU stable in a long pulse machine, when external damping is absent. A sufficiently strong nonlinear octupole focusing field may limit the BBU growth, however.