Negative Ion Extraction With Finite Element Solvers and Ray Maps

The negative ion production and extraction are critical aspects of the neutral beam injector for ITER, so that improvements in their physical understanding are expected to contribute to the optimization of the injector design. A self-consistent 2-D model of the formation and acceleration of a beam o...

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Bibliographic Details
Published in:IEEE transactions on plasma science 2008-08, Vol.36 (4), p.1581-1588
Main Authors: Cavenago, M., Veltri, P., Sattin, F., Serianni, G., Antoni, V.
Format: Article
Language:English
Subjects:
Acceleration
Beams (radiation)
Boundary conditions
Design optimization
Electric potential
Electrons
Finite element analysis
Finite element method
Finite element methods
Injectors
Ion beams
Ions
Mathematical analysis
Mathematical models
Meniscus
negative ion
Neutrons
Optimization
Particle beam injection
Particle beams
Plasma
Plasma accelerators
Plasma sheaths
Production
simulations
Solvers
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Summary:The negative ion production and extraction are critical aspects of the neutral beam injector for ITER, so that improvements in their physical understanding are expected to contribute to the optimization of the injector design. A self-consistent 2-D model of the formation and acceleration of a beam of negative ions (including the sheath) is presented here, with plasma presheath replaced by a boundary condition (on a so-called start line) consistent with the 1-D complete plasma equations. An equivalent volume production before the start line is assumed. Negative beam space charge is expressed in terms of a current modulus j Sigma (z,x), coupled to the adimensional electric potential u. Solution is obtained with a partial differential equation finite element solver for u and with an iterative approach for j Sigma . A continuous map of particle orbits or rays (efficiently generated by interpolation) is used to improve the traditional discrete ray tracing; moreover, beam edge resolution is refined. Results include detailed information on plasma meniscus and beam skin structure.
ISSN:0093-3813
1939-9375
DOI:10.1109/TPS.2008.927291