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| THCO-B02 |
Low Energy Beam Transport for Ion Beams Created by an ECR
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213 |
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- P. Spaedtke
GSI, Darmstadt
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It has been shown previously that the emittance of an ion beam, extracted from an Electron Cyclotron Resonance Ion Source (ECRIS) is determined by magnetic field, applied electric potentials, geometry, and particle density together with the initial properties of these particles. The model used for computer simulation seems to fit the experimental results: ions are extracted from the ion source if they are created (started) at places where magnetic field lines are going through the extraction aperture. Furthermore, the absolute value of magnetic flux density relative to the flux density at the extraction aperture defines, whether this ion can be extracted. Due to coupling between the different projections of phase space because of the magnetic field, several assumptions used for beam transport issues are not valid any more. With increasing extracted currents, space charge compensation of the extracted beam becomes an important issue. This compensation will build up in a relatively short time, depending on the pressure, as long no leackage is present within the beam line.
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Slides
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| THCO-B03 |
Improved ECR Extraction and Transport Simulations Using Experimentally Measured Plasma Sputtering
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219 |
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- D. S. Todd, D. Leitner, C. M. Lyneis
LBNL, Berkeley, California
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Funding: Work supported by the Director, Office of Energy Research, Office of High Energy & Nuclear Physics, Nuclear Physics Division of the U. S. Department of Energy under Contract DE AC03-76SF00098.
Simulations of beam extraction across a plasma sheath in an ECR ion source are critically dependent upon ion density distributions at the plasma extracting face; however, these distributions have not been measured experimentally. We present a new method of defining the initial distributions for simulation based upon the measurement of biased disc sputter marks. Multi-species beam extraction and transport simulations using these initial conditions will be compared with beam imaging and emittance measurements from the superconducting ECR VENUS at several positions along the beam line illustrating this simple model's ability to reproduce measured beam characteristics such as beam hollowing even though the triangular distributions at plasma extraction are of nearly constant density. The various possible sources of the beam hollowing observed both in simulation and experiment will be discussed. In addition, we will present a generalized method to define the initial distribution at extraction using only magnetic field line tracing and extracting aperture geometry.
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Slides
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| THCO-B04 |
Three Dimensional Simulation of Ion Beam Extraction from an ECR Ion Source
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220 |
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- S. M. Elliott, E. K. White
LLT, Boulder
- O. Delferriere
CEA, Gif-sur-Yvette
- J. Simkin
Vector Fields Ltd., Oxford
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Prediction of ECR ion extraction behavior is important for high current density operation and beam transport calculations. In this paper we review the combined electric and magnetic field space charge beam simulation of ion beam formation from an ECR ion source with a multi-electrode extraction system. Included in the simulation is the influence of secondary charged particles generated by ion collisions in the residual gas on the space charge in the beam. The self-consistent space charge simulation uses a finite element method incorporates non-linear magnetic materials, a plasma free surface emission model, and the generation of secondary charged particles. This method is useful for predicting the ion beam behavior from the ECR ion source under conditions of varying current density, electrode potential, and background gas pressure, including the behavior of suppressed electron flow and the influence of magnetic fields.
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Slides
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