Particle pinch with fully noninductive lower hybrid current drive in Tore Supra

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Nuclear Fusion

Background:

• Sustaining steady-state plasmas is critical for future fusion power plants.
• Lower Hybrid Current Drive (LHCD) is a key technique for non-inductive plasma current sustainment.
• Understanding particle transport mechanisms is essential for controlling plasma density profiles.

Purpose of the Study:

• To investigate particle transport in steady-state plasmas generated by LHCD.
• To determine the existence and magnitude of particle pinch effects in the absence of a toroidal electric field.
• To compare experimental observations with predictions from neoclassical theory.

Main Methods:

• Achieving long-duration (over 4 minutes) steady-state plasmas using LHCD in the Tore Supra tokamak.
• Operating under conditions where the neoclassical particle pinch driven by the toroidal electric field is negligible.
• Analyzing the plasma density profiles to identify particle transport behavior.

Main Results:

• Demonstrated sustained peaked plasma density profiles for over 4 minutes in LHCD-driven plasmas.
• Observed an inward particle pinch effect significantly larger than predicted by collisional neoclassical theory.
• Confirmed the existence of this pinch in the absence of a toroidal electric field.

Conclusions:

• The study experimentally validates a strong inward particle pinch in steady-state plasmas, independent of the neoclassical pinch driven by toroidal electric fields.
• These findings suggest that other mechanisms contribute significantly to particle transport in fusion plasmas.
• The results have important implications for controlling and optimizing plasma density in future fusion reactors.