Upgrades to the in-vessel calibration light source on JET

Area of Science:

• Fusion Energy Research
• Plasma Diagnostics
• Optical Engineering

Background:

• The Joint European Torus (JET) utilizes an in-vessel calibration light source (ICLS) for diagnostic calibration across UV, visible, and IR wavelengths.
• The ICLS is an integrating sphere positioned within the vacuum vessel using a remote handling (RH) system during shutdowns.

Purpose of the Study:

• To enhance the efficiency, quality, and operational flexibility of the ICLS system at JET.
• To improve spectral radiance uniformity and enable real-time verification of calibration light source performance.

Main Methods:

• Replaced a 20m umbilical cable with a 2m lightweight cable for direct connection to the RH manipulator.
• Integrated an on-board micro-spectrometer for real-time spectral verification.
• Installed new baffles within the integrating sphere to improve spectral radiance uniformity.

Main Results:

• Reduced calibration deployment time and improved operational flexibility by eliminating the need for vessel access floor installation.
• Enabled compatibility with calibrations following high neutron-fluence operations.
• Significantly improved spectral radiance uniformity at non-normal viewing angles, compensating for RH orientation uncertainties.

Conclusions:

• The upgraded ICLS system at JET demonstrates enhanced performance and operational efficiency.
• The modifications ensure reliable and accurate diagnostic calibration, even after intense operational periods.
• The improved uniformity and real-time verification contribute to more robust fusion energy research.