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H-Mode operation in the START spherical tokamak
1EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB, United Kingdom.
Physical Review Letters
|October 4, 2000
Summary
High-current spherical tokamak plasmas achieved H-mode operation, demonstrating improved energy confinement. This breakthrough signifies enhanced performance in spherical tokamak research.
Area of Science:
- Plasma physics
- Fusion energy research
- Tokamak engineering
Background:
- The spherical tokamak (ST) offers a compact, high-field alternative for fusion energy.
- Achieving high-performance plasma regimes like H-mode is crucial for ST development.
- Previous ST experiments faced challenges in reaching H-mode parameters.
Purpose of the Study:
- To demonstrate and characterize H-mode operation in the START spherical tokamak.
- To investigate the plasma physics associated with H-mode transitions in STs.
- To assess the impact of H-mode on energy confinement time in high-current ST plasmas.
Main Methods:
- Utilizing the START spherical tokamak with plasma currents exceeding 200 kA.
- Employing both neutral beam injection heating and Ohmic heating methods.
- Analyzing plasma profiles to identify edge pedestals, transport barriers, and edge-localized modes.
Main Results:
- Successful achievement of H-mode operation in high-current (I(p)>200 kA) plasmas.
- Observation of distinct edge density and temperature pedestals, indicative of edge-transport barriers.
- Correlation of H-mode features with increased energy confinement time at plasma currents >250 kA.
Conclusions:
- This study provides the first clear demonstration of the H-mode regime in a spherical tokamak.
- The results validate the potential of STs for achieving enhanced plasma performance.
- Further research into ST H-mode physics can guide future fusion reactor designs.
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