Electromagnetic torque measurements in DIII-D using internal/external magnetic field decomposition

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Electromagnetism

Background:

• Accurate measurement of electromagnetic torque is crucial for understanding and controlling plasma behavior in fusion devices.
• Traditional methods often require detailed knowledge of internal and external current distributions, which can be challenging to obtain.

Purpose of the Study:

• To present a novel method for directly measuring electromagnetic torque on magnetically confined plasmas.
• To demonstrate the utility of decomposing magnetic fields into plasma and external contributions for torque analysis.

Main Methods:

• Utilizing spatially resolved measurements of magnetic field components (normal and tangential) outside the plasma surface.
• Decomposing the measured magnetic field into contributions from the plasma and external sources.
• Applying this decomposition to calculate electromagnetic torque without prior knowledge of current distributions.

Main Results:

• The proposed method allows for unique decomposition of the magnetic field, enabling direct torque measurement.
• This approach is analogous to the Maxwell stress tensor formalism but offers flexibility.
• Experimental data from the DIII-D tokamak on torque evolution during tearing mode locking aligns with the developed model.

Conclusions:

• The internal/external field decomposition provides a direct and model-independent way to measure electromagnetic torque.
• This technique can be integrated with known current distributions for enhanced analysis.
• The findings support the applicability of this method for studying plasma dynamics, particularly in scenarios like tearing mode locking.