Millimeter-wave high-wavenumber scattering diagnostic developments on EAST and NSTX-U

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Diagnostic Development

Background:

• The Experimental Advanced Superconducting Tokamak (EAST) requires advanced diagnostics to study plasma behavior.
• Understanding high-k electron density fluctuations is crucial for controlling plasma instabilities in fusion devices.
• Existing diagnostic capabilities may be limited in probing small-scale turbulence.

Purpose of the Study:

• To develop and implement a novel 4-channel, high-k poloidal millimeter-wave collective scattering system for EAST.
• To measure high-k electron density fluctuations and their poloidal wavenumber spectrum (kθ).
• To investigate ion and electron-scale plasma instabilities, including the electron temperature gradient (ETG) mode.

Main Methods:

• Deployment of a 270 GHz mm-wave probe beam across specific ports on the EAST tokamak.
• Utilizing large aperture optics to capture scattered radiation at four simultaneous angles.
• Development of beam tracing and data interpretation modules tailored for high-k scattering diagnostics.

Main Results:

• Successful development and laboratory testing of the 4-channel, high-k poloidal scattering system.
• The system is designed to measure poloidal wavenumbers up to 20 cm-1.
• Installation on EAST is currently underway, enabling in-situ measurements.

Conclusions:

• The new high-k scattering system significantly enhances EAST's capability to probe small-scale electron density fluctuations.
• This diagnostic advancement will provide crucial data for understanding and mitigating plasma instabilities.
• The developed modules are also applicable to other tokamak facilities like NSTX-U.