Simulation of space charge compensation in a multibeamlet negative ion beam

E. Sartori, T.J. MacEina, P. Veltri, M. Cavenago, G. Serianni

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Ion beam space charge compensation occurs by cumulating in the beam potential well charges having opposite polarity, usually generated by collisional processes. In this paper we investigate the case of a H-ion beam drift, in a bi-dimensional approximation of the NIO1 (Negative Ion Optimization phase 1) negative ion source. H-beam ion transport and plasma formation are studied via particle-in-cell simulations. Differential cross sections are sampled to determine the velocity distribution of secondary particles generated by ionization of the residual gas (electrons and slow H2+ions) or by stripping of the beam ions (electrons, H, and H+). The simulations include three beamlets of a horizontal section, so that multibeamlet space charge and secondary particle diffusion between separate generation regions are considered, and include a repeller grid biased at various potentials. Results show that after the beam space charge is effectively screened by the secondary plasma in about 3 μs (in agreement with theoretical expectations), a plasma grows across the beamlets with a characteristic time three times longer, and a slight overcompensation of the electric potential is verified as expected in the case of negative ions.
Original languageEnglish
Article number02B917
Pages (from-to)-
JournalReview of Scientific Instruments
Issue number2
Publication statusPublished - 1 Feb 2016
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Instrumentation

Cite this

Sartori, E., MacEina, T. J., Veltri, P., Cavenago, M., & Serianni, G. (2016). Simulation of space charge compensation in a multibeamlet negative ion beam. Review of Scientific Instruments, 87(2), -. [02B917].