Assessment of the Structural Vibration Effect on Plasma Current Measurement Using a Fiber Optic Current Sensor in...

Area of Science:

• Fusion energy research
• Optical sensing technologies

Background:

• Accurate plasma current measurement is critical for ITER operation.
• Fiber Optic Current Sensors (FOCS) are a key technology for ITER diagnostics.
• Environmental factors like vibrations can potentially affect sensor accuracy.

Purpose of the Study:

• To evaluate the impact of cryostat bridge vibrations on FOCS accuracy in ITER.
• To investigate how vibrations affect the light polarization state within the FOCS.
• To determine if FOCS can meet ITER's stringent plasma current measurement requirements under operational vibrations.

Main Methods:

• Experimental investigation of vibration effects on a miniaturized FOCS mock-up.
• Numerical simulation of the FOCS setup using the Jones matrix approach.
• Incorporation of experimentally derived vibration matrices into numerical models.

Main Results:

• Vibrations induce changes in the light polarization state within the FOCS.
• The use of low-birefringent spun optical fiber significantly reduces the impact of these polarization changes.
• Simulations confirmed that vibration effects are manageable with appropriate fiber selection.

Conclusions:

• Cryostat bridge vibrations do not preclude the use of FOCS for accurate plasma current measurement in ITER.
• The selection of low-birefringent spun optical fiber is crucial for maintaining FOCS accuracy.
• ITER's plasma current measurement accuracy requirements can be met with the proposed FOCS configuration.