New compact and efficient local oscillator optic system for the KSTAR electron cyclotron emission imaging system

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Diagnostic Techniques

Background:

• Electron Cyclotron Emission Imaging (ECEI) is crucial for measuring electron temperature (Te) fluctuations in fusion plasmas.
• Current ECEI systems use cylindrical lens optics with a long optical path length (OPL) of 2-2.5 m.
• This long OPL can limit coupling efficiency, especially at plasma edges.

Purpose of the Study:

• To propose and evaluate a compact local oscillator (LO) optics design for the ECEI diagnostic.
• To reduce the OPL of the LO source for improved efficiency and compactness.
• To enhance the coupling efficiency of the LO source, particularly for edge plasma measurements.

Main Methods:

• Utilizing a Powell lens for the LO optics to achieve a significantly reduced OPL (0.4 m).
• Conducting optical simulations to predict performance.
• Performing laboratory tests on a prototype optics system.

Main Results:

• The proposed Powell lens optics reduces the OPL from ~2.0 m to 0.4 m.
• Optical simulations indicate improved coupling efficiency, especially for edge plasma channels.
• Laboratory tests of the prototype optics are expected to validate simulation results.

Conclusions:

• The Powell lens offers a more compact and efficient solution for ECEI LO optics.
• This advancement is expected to enhance the measurement capabilities of the ECEI diagnostic.
• The findings contribute to the development of advanced diagnostics for fusion research.