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Title: Space-charged-induced emittance growth in the transport of high-brightness electron beams

Abstract

The emittance induced by space charge in a drifting beam of finite length has been investigated, and a scaling law has been obtained from simple considerations of the different rates of expansion of different portions of the beam. The scaling law predicts the initial rate of emittance growth, before the beam shape has distorted significantly, and thus represents an upper bound on the rate of emittance increase. This scaling law has been substantiated by particle-in-cell simulation and the dependence on geometric factors evaluated for specific choices of the beam profile. For long, axially nonuniform beams, the geometric factors have been evaluated explicitly for Gaussian profiles, and other shapes.

Authors:
;
Publication Date:
Research Org.:
Los Alamos National Lab., NM (USA)
OSTI Identifier:
6643237
Report Number(s):
LA-UR-87-415; CONF-870302-62
ON: DE87007460
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Particle accelerator conference, Washington, DC, USA, 16 Mar 1987; Other Information: Paper copy only, copy does not permit microfiche production
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; BEAM EMITTANCE; SCALING LAWS; ELECTRON BEAMS; SPACE CHARGE; ANALYTICAL SOLUTION; BRIGHTNESS; COMPUTERIZED SIMULATION; BEAMS; LEPTON BEAMS; OPTICAL PROPERTIES; PARTICLE BEAMS; PHYSICAL PROPERTIES; SIMULATION 430200* -- Particle Accelerators-- Beam Dynamics, Field Calculations, & Ion Optics

Citation Formats

Jones, M.E., and Carlsten, B.E. Space-charged-induced emittance growth in the transport of high-brightness electron beams. United States: N. p., 1987. Web.
Jones, M.E., & Carlsten, B.E. Space-charged-induced emittance growth in the transport of high-brightness electron beams. United States.
Jones, M.E., and Carlsten, B.E. 1987. "Space-charged-induced emittance growth in the transport of high-brightness electron beams". United States. doi:. https://www.osti.gov/servlets/purl/6643237.
@article{osti_6643237,
title = {Space-charged-induced emittance growth in the transport of high-brightness electron beams},
author = {Jones, M.E. and Carlsten, B.E.},
abstractNote = {The emittance induced by space charge in a drifting beam of finite length has been investigated, and a scaling law has been obtained from simple considerations of the different rates of expansion of different portions of the beam. The scaling law predicts the initial rate of emittance growth, before the beam shape has distorted significantly, and thus represents an upper bound on the rate of emittance increase. This scaling law has been substantiated by particle-in-cell simulation and the dependence on geometric factors evaluated for specific choices of the beam profile. For long, axially nonuniform beams, the geometric factors have been evaluated explicitly for Gaussian profiles, and other shapes.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1987,
month = 3
}

Conference:
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  • We report our initial measurements of bright (high-charge, low-emittance) electron beams generated at the Los Alamos High Brightness Accelerator FEL (HIBAF) Facility. Normalized emittance values of less than 50 {pi} mm-mrad for charges ranging from 0.7 to 8.7 nC were obtained for single micropulses at a y-waist and at an energy of 14.7 MeV. These measurements were part of the commissioning campaign on the HIBAF photoelectric injector. Macropulse measurements have also been performed and are compared with PARMELA simulations. 5 refs., 8 figs., 3 tabs.
  • The rms emittance increase of high current beams in transport lines, caused by nonlinear space charge forces, can be understood as the development of the initial particle distribution to an equilibrium one. For a small beam radius, one gets less rms emittance increase and the equilibrium distribution is reached earlier than for a large beam radius. The beam can now be transported over a long distance without further rms emittance growth in all 3 directions. These results are incorporated in the design of a funneling section for the high current linear accelerator of the HIBALL concept.
  • The systematic study of the dependence of the charge state density distribution (CSDD) on the discharge parameters of both the duopigatron and the duoplasmatron sources was conducted. The experimental data show that for both sources the optimum conditions for multiply-charged ion production correspond to the operation of the discharge at points between two different modes. In particular, the pressure must be matched to a minimum value corresponding to the arc starvation mode. Under this condition the discharge exhibits large level fluctuations which are correlated with enlarged ion energy spreads. However, the instability level can (particularly in the duopigatron) be minimizedmore » by a proper choice of the magnetic field shape and magnetic field strength. In order to describe more completely the source performances, the emittance and brightness were measured under optimum conditions for production of multiply-charged ions in our design. Solutions were proposed to improve emittance and brightness by the adaptation of a plasma expansion cup. These solutions do not inversely affect the CSDD. The obtained performances are compared with other experiments.« less
  • These proceedings represent papers presented at the Workshop on space charge dominated beams, approved by the ICFA beam dynamics panel. The workshop took a closer look at the major breakthroughs occurring in the past few years. The topics discussed include experiments with space charge dominated beams and halo formation, statistical and Fokker{minus}Planck methods, neutron spallation sources, heavy ion inertial fusion, and high brightness electron beams. There were 39 papers presented at the workshop and all 39 have been abstracted for the Energy Science and Technology database.(AIP)