Rhodium coated mirrors deposited by magnetron sputtering for fusion applications

Area of Science:

• Materials Science
• Plasma Physics
• Optical Engineering

Background:

• Metallic mirrors are critical for ITER plasma diagnostics.
• Mirror performance degradation (reflectivity loss) impacts signal quality.
• Rhodium is a promising material due to high reflectivity and low sputtering yield.

Purpose of the Study:

• Develop a reliable technique for preparing high-reflectivity rhodium films.
• Evaluate rhodium films as a cost-effective alternative for ITER mirrors.
• Assess the performance and durability of rhodium-coated mirrors.

Main Methods:

• Magnetron sputtering was used to deposit rhodium films (up to 2 microm) onto various substrates (Mo, stainless steel, Cu).
• Film properties (roughness, crystallite size, structure, impurities) were analyzed.
• Scratch tests evaluated adhesion, and optical characterizations assessed reflectivity.
• Erosion tests were conducted under laboratory conditions and in the TEXTOR tokamak.

Main Results:

• Dense columnar rhodium films with low roughness and ~10 nm crystallite size were produced.
• No surface impurities were detected after deposition.
• Adhesion improved with substrate hardness.
• Optical characterizations and erosion test results were detailed.

Conclusions:

• Magnetron-sputtered rhodium films are suitable for ITER first mirrors.
• The developed technique yields high-quality films with good adhesion and reflectivity.
• Rhodium films offer a durable and reliable solution for plasma diagnostic systems.