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Introduction

Space-charge compensation is routinely used in linacs and rf photoinjectors. In rings, it would enable higher intensities.

It is a challenging subject: is it possible to mitigate a global effect (space-charge repulsion) with a local correction?
Issues include the need for high charge densities, unwanted lattice distortions, and beam-plasma instabilities.

ecolumn_concept_2.png
Electron-column concept

Implementation with an electron lens has advantage of magnetic confinement for stability. Two concepts were developed:

  • generating a given current profile (transverse and possibly longitudinal) from the electron gun or
  • trapping electrons from residual-gas ionization in a Penning-Malmberg configuration (electron column).

Numerical simulation studies are necessary to guide experiments in IOTA.

Physics of space-charge compensation in rings

Early experimental studies demonstrated higher intensities or desired tune shift, but
also instabilities:

  • Dimov and Chupriyanov, Part. Accel. 14, 155 (1984) (BINP PSR, no confinement)
  • Shiltsev et al., PAC09 (Tevatron, limited parameters and diagnostics)

Simulations with rigid e-columns show benefits on emittances and lifetimes, but
also lattice distortions and resonances, depending on the number of devices:

  • Burov et al., FERMILAB-TM-2125 (2000) [Fermilab Booster]
  • Alexahin and Kapin, Fermilab Beam-docs 3108 (2008) [Fermilab Booster]
  • Aiba et al., PAC07 [LHC injectors]
  • Boine-Frankenheim and Stem, NIM A 896, 122 (2018) [GSI SIS]
  • Stern et al., Beams-doc-6790 (2018) [Fermilab RCS model]

A campaign of self-consistent simulations was started for IOTA:

  • Single pass, with gas ionization: Park et al., NAPAC16
  • Two passes, no lattice: Freemire et al., HB18
  • Multi-pass integration Synergia+Warp: Freemire et al., IPAC19

Next steps include:

  • linear and nonlinear lattices between passes
  • electron-ion recombination
  • plasma collisions and thermalization

Numerical simulations

Related projects

Previous work by Chong Shik Park, Diletta Milana and others: https://cdcvs.fnal.gov/redmine/projects/ecolumns

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