Scrape-off layer reflectometer for Alcator C-Mod

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Diagnostic Systems

Background:

• Accurate measurement of plasma density is critical for fusion energy research.
• The scrape-off layer (SOL) region in tokamaks influences plasma confinement and requires detailed profiling.
• Existing diagnostic limitations necessitate new methods for SOL density measurements.

Purpose of the Study:

• To develop and implement a swept-frequency X-mode reflectometer for Alcator C-Mod.
• To measure SOL density profiles at multiple locations near new plasma heating systems.
• To characterize the performance and minimize losses in the reflectometer's transmission line system.

Main Methods:

• Utilizing swept-frequency X-mode reflectometry operating between 100-146 GHz.
• Employing both differential phase and full phase reflectometry to mitigate density fluctuation effects.
• Designing and simulating tallguide (TE(01)) components for low-loss signal transmission.

Main Results:

• The system is designed to cover a density range of 10^16-10^20 m^-3 at magnetic fields of 5-5.4 T.
• Simulations demonstrate high mode conversion efficiency in tallguide components.
• Experimental measurements of attenuation losses in waveguide components will be presented.

Conclusions:

• The developed X-mode reflectometer will provide crucial data for understanding SOL physics in Alcator C-Mod.
• The use of tallguide technology minimizes signal attenuation, improving measurement accuracy.
• This diagnostic advancement supports ongoing fusion energy research efforts.