Local current density measurement using a Rogowski probe in Tokyo Spherical Tokamak-2

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Diagnostic Instrumentation

Background:

• Accurate measurement of local current density is crucial for understanding plasma confinement and stability in fusion devices.
• Previous diagnostic methods may have limitations in spatial resolution or directional sensitivity.

Purpose of the Study:

• To develop and validate a novel Rogowski probe for measuring local current density and its direction.
• To investigate the current density profile near the last closed flux surface in Ohmic plasmas.

Main Methods:

• Development of a multi-layer Rogowski coil integrated with magnetic pick-up coils and a Langmuir probe.
• Implementation of a movable and rotatable probe system for detailed spatial mapping.
• Application of the probe in the Tokyo Spherical Tokamak-2 (TST-2) Ohmic plasma experiments.

Main Results:

• Successful measurement of the local current density and its direction using the developed probe.
• Acquisition of the current density profile near the last closed flux surface.
• Achieved a high signal-to-noise ratio (greater than 20) for the measurements.

Conclusions:

• The developed Rogowski probe is an effective diagnostic tool for precise current density measurements in tokamak plasmas.
• The probe's mobility and directional sensitivity allow for detailed profiling critical for fusion research.
• The successful application in TST-2 demonstrates its utility in studying plasma behavior.