Density modulation experiment to determine transport coefficients on Joint-TEXT Tokamak

Area of Science:

• Plasma physics
• Fusion energy research
• Tokamak diagnostics

Background:

• Understanding particle transport is crucial for achieving stable fusion conditions in tokamaks.
• Density modulation techniques provide insights into plasma behavior and confinement properties.

Purpose of the Study:

• To investigate particle transport in Joint-TEXT (J-TEXT) Tokamak Ohmic discharges.
• To validate a new three-wave polarimeter-interferometer system (POLARIS) for measuring perturbed plasma density.
• To analyze the relationship between particle confinement time and electron density.

Main Methods:

• Density modulation experiments were performed on the J-TEXT Tokamak.
• Perturbed plasma density was measured using both a HCN interferometer and the newly developed POLARIS system.
• Data analysis employed a model with constant diffusion plus inward convection.

Main Results:

• Consistent measurements of perturbed density were obtained from both the HCN interferometer and POLARIS.
• The analysis scheme for particle transport was validated by the agreement between the two diagnostic systems.
• Particle confinement time (τp) was observed to increase with electron density at lower densities.
• Particle confinement time saturated at higher electron densities.

Conclusions:

• The POLARIS system is a valid and reliable diagnostic for measuring perturbed plasma density in tokamaks.
• Particle transport in J-TEXT Tokamak Ohmic discharges exhibits density-dependent behavior, with saturation of confinement time at higher densities.
• The findings contribute to a better understanding of particle confinement in fusion devices.