Electron cloud effects in intense, ion beam linacs theory and experimental planning for heavy-ion fusion

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Heavy-ion accelerators for HIF will operate at high aperture-fill factors with high beam current and long pulses. This will lead to beam ions impacting walls: liberating gas molecules and secondary electrons. Without special preparation a large fractional electron population ({approx}>1%) is predicted in the High-Current Experiment (HCX), but wall conditioning and other mitigation techniques should result in substantial reduction. Theory and particle-in-cell simulations suggest that electrons, from ionization of residual and desorbed gas and secondary electrons from vacuum walls, will be radially trapped in the {approx}4 kV ion beam potential. Trapped electrons can modify the beam space charge, vacuum pressure, ... continued below

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Molvik, A.W.; Cohen, R.H.; Lund, S.M.; Bieniosek, F.M.; Lee, E.P.; Prost, L.R. et al. May 21, 2002.

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Heavy-ion accelerators for HIF will operate at high aperture-fill factors with high beam current and long pulses. This will lead to beam ions impacting walls: liberating gas molecules and secondary electrons. Without special preparation a large fractional electron population ({approx}>1%) is predicted in the High-Current Experiment (HCX), but wall conditioning and other mitigation techniques should result in substantial reduction. Theory and particle-in-cell simulations suggest that electrons, from ionization of residual and desorbed gas and secondary electrons from vacuum walls, will be radially trapped in the {approx}4 kV ion beam potential. Trapped electrons can modify the beam space charge, vacuum pressure, ion transport dynamics, and halo generation, and can potentially cause ion-electron instabilities. Within quadrupole (and dipole) magnets, the longitudinal electron flow is limited to drift velocities (E x B and {del}B) and the electron density can vary azimuthally, radially, and longitudinally. These variations can cause centroid misalignment, emittance growth and halo growth. Diagnostics are being developed to measure the energy and flux of electrons and gas evolved from walls, and the net charge and gas density within magnetic quadrupoles, as well as the their effect on the ion beam.

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INIS; OSTI as DE00799650

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  • Laser and Particle Beams, Moscow (RU), 05/26/2002--05/31/2002

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  • Report No.: LBNL--51009
  • Grant Number: AC03-76SF00098
  • Office of Scientific & Technical Information Report Number: 799650
  • Archival Resource Key: ark:/67531/metadc742917

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  • May 21, 2002

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  • Oct. 19, 2015, 7:39 p.m.

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  • April 4, 2016, 3:11 p.m.

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Molvik, A.W.; Cohen, R.H.; Lund, S.M.; Bieniosek, F.M.; Lee, E.P.; Prost, L.R. et al. Electron cloud effects in intense, ion beam linacs theory and experimental planning for heavy-ion fusion, article, May 21, 2002; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc742917/: accessed August 20, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.