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Dual laser interferometer for plasma density measurements on large tokamaks
The Review of Scientific Instruments
|July 1, 1978
Summary
A novel two-wavelength plasma density interferometer using CO(2) and HeNe lasers distinguishes plasma density from mirror vibrations. This advanced system achieves precise measurements of plasma density fringe shifts, even amidst significant mirror disturbances.
Area of Science:
- Plasma physics
- Optical interferometry
- Fusion energy research
Background:
- Accurate measurement of plasma density is crucial for understanding and controlling fusion plasmas.
- Traditional interferometers struggle to differentiate plasma-induced fringe shifts from those caused by mechanical vibrations.
Purpose of the Study:
- To describe a two-wavelength plasma density interferometer designed for the Doublet III tokamak.
- To enable precise measurement of plasma density by mitigating interference from mirror vibrations.
Main Methods:
- Utilizing a dual-wavelength approach with a carbon dioxide (CO(2)) laser and a helium-neon (HeNe) laser.
- Implementing a simple digital phase-comparing electronic system for fringe shift analysis.
Main Results:
- Successfully distinguished fringe shifts caused by plasma density from those caused by mirror vibrations.
- Achieved measurement sensitivity of 1/10th of a fringe shift in the presence of multiple fringe shifts from vibrations.
Conclusions:
- The two-wavelength interferometer effectively overcomes the challenge of differentiating plasma density signals from mechanical noise.
- This technique offers a robust method for precise plasma density diagnostics in large fusion devices like tokamaks.
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