Real-time diamagnetic flux measurements on ASDEX Upgrade.

Area of Science:

• Plasma Physics
• Fusion Energy
• Magnetic Confinement Fusion

Background:

• Diamagnetic flux measurements are essential for understanding plasma behavior in tokamaks.
• Traditional methods often require complex analog signal summation, limiting accuracy and sensitivity.
• ASDEX Upgrade sought to implement a more direct and sensitive diamagnetic flux measurement technique.

Purpose of the Study:

• To introduce and validate a novel real-time diamagnetic flux measurement system on ASDEX Upgrade.
• To demonstrate the system's high sensitivity and accuracy by minimizing unwanted signal contributions.
• To compare experimental results with simulation predictions and established diagnostic codes.

Main Methods:

• Implementing real-time diamagnetic flux measurement with integrators triggered before plasma initiation.
• Utilizing a compensation coil system to negate external magnetic field influences.
• Performing identical plasma discharges with reversed magnetic fields to assess alignment errors.
• Comparing measured diamagnetic flux with TRANSP simulations and poloidal beta with equilibrium reconstruction codes.

Main Results:

• The new system provides real-time diamagnetic flux measurements on ASDEX Upgrade.
• No analog summation is required, simplifying the measurement and reducing error sources.
• Alignment errors with respect to plasma current were found to be negligible.
• Measurements show good agreement with TRANSP simulations and equilibrium reconstruction codes.

Conclusions:

• The developed real-time diamagnetic flux measurement system on ASDEX Upgrade is highly sensitive and accurate.
• This technique simplifies flux measurement and error compensation in tokamaks.
• The system's validation enables its use in conjunction with TRANSP simulations for advanced plasma diagnostics, particularly for estimating coupled power in ion cyclotron resonance heating scenarios.