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Title: Beam Halo formation and loss induced by image-charge effects in a small-aperture alternating-gradient focusing system

Abstract

Effects of image charges on beam halo formation and beam loss in small-aperture alternating-gradient focusing systems are studied analytically, computationally, and experimentally. Nonlinear image-charge fields result in chaotic particle motion and the ejection of particles from the beam core into a halo. Detailed chaotic particle motion and structure of the particle phase space is studied, and the beam loss rate is computed for a long transport channel. Image-charge effects are also studied for a short transport channel, and compared with the Neutralized Transport Experiment (NTX) at LBNL.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Director, Office of Science. Fusion Energy Sciences (US)
OSTI Identifier:
815519
Report Number(s):
LBNL-53082; HIFAN 1249
R&D Project: Z46010; TRN: US0304645
DOE Contract Number:
AC03-76SF00098
Resource Type:
Conference
Resource Relation:
Conference: Particle Accelerator Conference PAC 03, Portland, OR (US), 05/12/2003--05/16/2003; Other Information: PBD: 1 May 2003
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; 43 PARTICLE ACCELERATORS; ACCELERATORS; FOCUSING; PHASE SPACE; TRANSPORT

Citation Formats

Zhou, J., Qian, B.L., Chen, C., Henestroza, E., Eylon, S., and Yu S.. Beam Halo formation and loss induced by image-charge effects in a small-aperture alternating-gradient focusing system. United States: N. p., 2003. Web.
Zhou, J., Qian, B.L., Chen, C., Henestroza, E., Eylon, S., & Yu S.. Beam Halo formation and loss induced by image-charge effects in a small-aperture alternating-gradient focusing system. United States.
Zhou, J., Qian, B.L., Chen, C., Henestroza, E., Eylon, S., and Yu S.. 2003. "Beam Halo formation and loss induced by image-charge effects in a small-aperture alternating-gradient focusing system". United States. doi:. https://www.osti.gov/servlets/purl/815519.
@article{osti_815519,
title = {Beam Halo formation and loss induced by image-charge effects in a small-aperture alternating-gradient focusing system},
author = {Zhou, J. and Qian, B.L. and Chen, C. and Henestroza, E. and Eylon, S. and Yu S.},
abstractNote = {Effects of image charges on beam halo formation and beam loss in small-aperture alternating-gradient focusing systems are studied analytically, computationally, and experimentally. Nonlinear image-charge fields result in chaotic particle motion and the ejection of particles from the beam core into a halo. Detailed chaotic particle motion and structure of the particle phase space is studied, and the beam loss rate is computed for a long transport channel. Image-charge effects are also studied for a short transport channel, and compared with the Neutralized Transport Experiment (NTX) at LBNL.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2003,
month = 5
}

Conference:
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  • In space-charge dominated beams the nonlinear space-charge forces produce a filamentation pattern, which results in a 2-component beam consisting of an inner core and an outer halo. The halo is very prominent in mismatched beams, and the potential for accelerator activation is of concern for a next generation of cw, high-power proton linacs that could be applied for intense neutron generators to process nuclear materials. We present new results about beam halo and the evolution of space-charge dominated beams from multiparticle simulation of initial laminar beams in a uniform linear focusing channel, and from a model consisting of single particlemore » interactions with a uniform-density beam core. We study the energy gain from particle interactions with the space-charge field of the core, and we identify the resonant characteristic of this interaction as the basic cause of the separation of the beam into the two components. We identify three different particle-trajectory types, and we suggest that one of these types may lead to continuous halo growth, even after the halo is removed by collimators.« less
  • In space-charge dominated beams the nonlinear space-charge forces produce a filamentation pattern, which results in a 2-component beam consisting of an inner core and an outer halo. The halo is very prominent in mismatched beams, and the potential for accelerator activation is of concern for a next generation of cw, high-power proton linacs that could be applied for intense neutron generators to process nuclear materials. We present new results about beam halo and the evolution of space-charge dominated beams from multiparticle simulation of initial laminar beams in a uniform linear focusing channel, and from a model consisting of single particlemore » interactions with a uniform-density beam core. We study the energy gain from particle interactions with the space-charge field of the core, and we identify the resonant characteristic of this interaction as the basic cause of the separation of the beam into the two components. We identify three different particle-trajectory types, and we suggest that one of these types may lead to continuous halo growth, even after the halo is removed by collimators.« less
  • A test-particle model is used to investigate the charged-particle dynamics in an intense matched ion beam with nonuniform density profile propagating through an alternating-gradient quadrupole focusing field in the space-charge-dominated regime. It is shown that self-field nonlinearities due to the transverse nonuniformity in the beam density profile not only can result in chaotic ion motion but also can cause halo formation by the ejection of particles from the beam core. The structure of the particle phase space is studied. It is shown that the process of halo formation can occur on a fast time scale---on the order of a fewmore » lattice periods. The halo size is found to be determined by a Kolmogorov--Arnold--Moser (KAM) surface on a time scale much shorter than that of Arnold diffusion. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.« less
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  • A simple set of formulas is derived which relate emittance, line charge density, matched maximum and average envelope radii, occupancy factors, and the (space charge) depressed and vacuum values of tune. This formulation is an improvement on the smooth limit approximation; deviations from exact (numerically determined) relations are on the order of + or -2%, while the smooth limit values are in error by up to + or -30%. This transport formalism is used to determine the limits of transportable line charge density in an electrostatic quadrupole array, with specific application to the low energy portion of the High Temperaturemore » Experiment of Heavy Ion Fusion Accelerator Research. The line charge density limit is found to be essentially proportional to the voltage on the pole faces and the fraction of occupied aperture area. A finite injection energy (greater than or equal to 2 MeV) is required to realize this limit, independent of particle mass.« less