Development and initial results of 320 GHz interferometer system in Heliotron J.

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Applied Electromagnetics

Background:

• Heliotron J requires advanced diagnostics for high-density plasma studies.
• Existing interferometry methods face limitations in high-density environments.

Purpose of the Study:

• To install and validate a new 320 GHz solid-state source interferometer for electron density measurements in Heliotron J.
• To explore plasma physics in high-density regimes (ne > 2-3 × 10^19 m^-3) using advanced fueling techniques.

Main Methods:

• Utilized a Michelson-type heterodyne interferometer with two independent 320 GHz solid-state sources (up to 50 mW output).
• Achieved high time resolution measurements (<1 µs) by tuning source frequency (312-324 GHz) for fluctuation analysis.
• Conducted experiments in the Heliotron J helical device using advanced fueling techniques.

Main Results:

• Successfully measured line-averaged electron density in high-density plasma experiments.
• Demonstrated agreement between the new interferometer and a conventional microwave interferometer using a different chord.
• Validated the system's capability for routine electron density diagnostics.

Conclusions:

• The new 320 GHz interferometer is a reliable tool for electron density diagnostics in Heliotron J.
• The system facilitates the exploration of high-density plasma physics relevant to fusion energy.
• High time resolution capabilities enable detailed fluctuation measurements.