W-band system-on-chip electron cyclotron emission imaging system on DIII-D.

Area of Science:

• Plasma physics
• Fusion energy research
• Advanced diagnostics

Background:

• The DIII-D tokamak requires advanced diagnostics for electron temperature profiling.
• Previous Electron Cyclotron Emission Imaging (ECEI) systems used Schottky diode mixer arrays with limitations.
• Millimeter-wave integrated circuits offer potential for improved radiometer performance.

Purpose of the Study:

• To develop and implement a novel millimeter-wave system-on-chip (SoC) based ECEI system for enhanced plasma diagnostics.
• To upgrade the ECEI system for compatibility with International Thermonuclear Experimental Reactor (ITER)-relevant scenarios.
• To improve the accuracy and resolution of 2D electron temperature profile and fluctuation measurements.

Main Methods:

• Developed a W-band (75-110 GHz) receiver module integrating low noise amplifiers, mixers, and local oscillator (LO) multipliers on a single die.
• Designed a 20-module horn-waveguide receiver array for the ECEI system.
• Incorporated an internal multiplier chain to downconvert the LO frequency for coaxial coupling.
• Utilized horn-waveguide shielding to prevent out-of-band noise interference.

Main Results:

• The upgraded W-band ECEI system demonstrated over 30 dB additional gain compared to previous systems.
• Achieved a 20x improvement in noise temperature over Schottky diode mixer input systems.
• Successfully deployed the upgraded system on the DIII-D tokamak for operational campaigns.
• Enabled precise 2D electron temperature profile and fluctuation evolution measurements.

Conclusions:

• The monolithic millimeter-wave SoC technology significantly enhances ECEI system performance for plasma diagnostics.
• The upgraded system provides crucial data for understanding edge and core region transport physics in fusion devices.
• This advancement is vital for ITER-relevant plasma control and research.