High-heat flux ball-pen probe head in ASDEX-Upgrade.

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Diagnostic Techniques

Background:

• Investigating the plasma edge in fusion devices like ASDEX-Upgrade (AUG) is crucial for understanding plasma confinement.
• Harsh plasma conditions, such as low power H-mode, require robust diagnostic tools.
• Existing probes face limitations in high heat flux environments.

Purpose of the Study:

• To introduce and evaluate a new high heat flux ball-pen probe head for ASDEX-Upgrade.
• To enable simultaneous measurement of multiple plasma parameters with high temporal resolution.
• To develop and apply a novel method for correcting sheath potential, accounting for secondary electron emission.

Main Methods:

• Installation and utilization of a novel multi-pin probe head (four Langmuir, two Mach, three ball-pen probes) on the AUG midplane manipulator.
• Development of a dynamic sheath potential correction method incorporating total secondary electron emission.
• Utilizing particle-in-cell simulations to determine secondary electron emission yield under AUG conditions and realistic impact angles.

Main Results:

• The new probe head successfully operates under high heat flux conditions, allowing plasma edge investigation in low power H-mode.
• Simultaneous measurement of plasma parameters including electron temperature and plasma potential profiles.
• Validation of a novel sheath potential correction method.

Conclusions:

• The high heat flux ball-pen probe head is a capable diagnostic for studying the plasma edge in challenging fusion reactor conditions.
• The developed method for secondary electron emission correction enhances the accuracy of plasma parameter measurements.
• The probe is suitable for investigating plasma turbulence around the separatrix in ASDEX-Upgrade.