The National Spherical Torus Experiment-Upgrade poloidal high-k scattering system pitch angle design modifications

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Wave Phenomena in Plasmas

Background:

• The National Spherical Torus Experiment-Upgrade (NSTX-U) requires advanced diagnostics to study plasma turbulence.
• Previous 280 GHz tangential scattering systems had limitations in measuring high-wavenumber (high-k) phenomena.
• Understanding electron density fluctuations is crucial for controlling plasma confinement in fusion devices.

Purpose of the Study:

• To develop and present a new 693 GHz, eight-channel, poloidal collective scattering system for the NSTX-U.
• To enable the study of high-k electron density fluctuations and their impact on plasma stability.
• To provide measurements of the k-theta spectrum for electron and ion temperature gradient modes.

Main Methods:

• Development of an eight-channel, poloidal collective scattering system operating at 693 GHz.
• Creation of a computational tool to calculate wavenumbers in strong magnetic pitch angles.
• Design of a new receiver optical system motivated by the wavenumber calculation tool.

Main Results:

• The new system will replace the older 280 GHz system, offering enhanced capabilities.
• The developed tool aids in understanding wavenumber behavior in complex magnetic geometries.
• The new optical design is expected to significantly improve system performance.

Conclusions:

• The 693 GHz poloidal scattering system represents a significant upgrade for NSTX-U diagnostics.
• Accurate measurement of high-k fluctuations is essential for advancing fusion energy research.
• The innovative optical design promises enhanced data acquisition and analysis for plasma turbulence studies.