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Updated: May 24, 2026
06:53
Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−
Published on: July 27, 2018
Sheath structure in negative ion sources for fusion (invited)
R McAdams1, D B King, A J T Holmes
1EURATOM∕CCFE Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB, United Kingdom. roy.mcadams@ccfe.ac.uk
The Review of Scientific Instruments
|March 3, 2012
Summary
A virtual cathode limits negative ion flux in fusion sources. A new 1D model accounts for this virtual cathode, improving understanding of negative ion transport across the plasma sheath.
Area of Science:
- Plasma physics
- Fusion energy research
Background:
- Negative ions are crucial for fusion energy.
- Formation occurs on caesiated plasma grids via hydrogen atoms.
- Space charge effects can limit ion flux.
Purpose of the Study:
- To present a 1D collisionless model of the plasma sheath.
- To incorporate the effect of a virtual cathode on negative ion transport.
- To apply the model to ion source operation and compare with experimental data.
Main Methods:
- Developed a 1D collisionless sheath model.
- Included space charge effects and virtual cathode formation.
- Extended the model to the bulk plasma region.
Main Results:
- The virtual cathode limits negative ion flux.
- The model shows good agreement with experimental data when extended to the bulk plasma.
- Identified a potential role for fast ions in the process.
Conclusions:
- The developed model accurately describes negative ion transport in fusion sources.
- Virtual cathode formation is a key limitation for negative ion emission.
- Further investigation into fast ion roles is warranted.
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