The digital mirror Langmuir probe: Field programmable gate array implementation of real-time Langmuir probe biasing

Area of Science:

• Plasma physics
• Fusion energy research
• Diagnostic techniques

Background:

• High-resolution measurements of electron temperature, density, and plasma potential are crucial for understanding tokamak boundary plasma turbulence.
• Conventional Langmuir probes face limitations in temporal or spatial resolution for these demanding measurements.

Purpose of the Study:

• To develop and implement a digital Mirror Langmuir Probe (MLP) controller for enhanced plasma diagnostics.
• To overcome the resolution limitations of traditional probe techniques in tokamak research.

Main Methods:

• Utilized a Field Programmable Gate Array (FPGA) board for a new digital MLP controller prototype.
• The controller rapidly switches voltage across three dynamically optimized bias states for single-electrode measurements.
• Simulated probe current response using experimental data on a second FPGA board for testing.

Main Results:

• The digital MLP controller successfully reproduces the functionality of the analog system, enabling high-speed data acquisition at 1.1 MSPS.
• FPGA technology allows for customizable, cost-effective, and time-efficient development.
• The system demonstrates potential for external plasma parameter feedback control.

Conclusions:

• The digital MLP controller represents a significant advancement in plasma diagnostic capabilities for fusion research.
• FPGA implementation offers flexibility, scalability, and reduced development costs.
• The project's availability as a git repository encourages collaboration and further development.