Turbulence level effects on conventional reflectometry using 2D full-wave simulations

Area of Science:

• Plasma Physics
• Wave Propagation
• Computational Electromagnetics

Background:

• Microwave diagnostics are essential for understanding plasma behavior.
• Turbulent plasmas present challenges for accurate diagnostic measurements.
• Numerical simulations are key to advancing diagnostic techniques.

Purpose of the Study:

• To apply the 2D finite-difference time-domain (FDTD) code REFMUL to simulate turbulent plasmas.
• To investigate the effects of plasma density turbulence on O-mode reflectometry signals.
• To explore the potential for extending measurement capabilities of plasma diagnostics.

Main Methods:

• Utilized the REFMUL code for 2D full-wave simulations.
• Modeled plasma density as a sum of background and fluctuating components with a Kolmogorov-like spectrum.
• Simulated O-mode waves with fixed frequency probing and I/Q detection.
• Scanned density turbulence levels and simulated plasma flows in radial and poloidal directions.

Main Results:

• Observed spectral broadening of complex signals and increased fluctuations in amplitude and phase with higher turbulence.
• Demonstrated similar trends for both radial and poloidal plasma flow directions.
• Identified the onset of non-linear effects, including phase runaway and radial Doppler effects.

Conclusions:

• The REFMUL code effectively simulates turbulent plasmas for reflectometry.
• Simulation results show promise for reconstructing poloidal wavenumber spectra.
• Findings contribute to enhancing the measuring capabilities of microwave diagnostics for turbulent plasmas.