Validation of Negative Ion Beam Space Charge Compensation

M. Cavenago[1], and P. Veltri[2]
[1]INFN-LNL, Legnaro, Italy
[2]RFX Consortium, Padova, Italy
Published in 2011

The transport of intense ion beams with reduced beam divergence over reasonable drift distances requires a reliable space charge compensation (SCC). Negative ion beams (required in the Neutral Beam Injectors envisioned for the ITER tokamak) are here discussed. Secondary particles are generated by beam-gas collisions within the beam volume and their motion is followed by explicit leapfrog time integration; a fraction of the particle exiting the lateral boundaries is injected again.

Poisson equation is solved and fields are accurately retrieved by Comsol Multiphysics at each time integration step; accurate choice of simulation parameters and speeding up techniques are used. Results show the formation of a SCC channel where the beam passes, after a short transition region at drift begin.

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