Progress of CO2 Dispersion Interferometer on EAST

A CO2 Dispersion Interferometer (DI) system on the Experimental Advanced Superconducting Tokamak (EAST) was successfully operated, providing plasma electron density measurements. The DI system utilizes a continuous-wave 9.3 μm CO2 laser source to measure line-averaged electron densities. This offers...

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Bibliographic Details
Published in:Journal of instrumentation 2024-04, Vol.19 (4), p.C04021
Main Authors: Liu, Y.Y., Li, W.M., Liu, H.Q., Lian, H., Yao, Y., Zhang, J.M., Zhang, Y., Hong, B., Wang, S.X., Yang, J.H., Jie, Y.X.
Format: Article
Language:English
Subjects:
Carbon dioxide
Carbon dioxide lasers
Continuous radiation
Control systems
Discharge
Electron density measurement
Feedback
High density
Interferometers
Nuclear instruments and methods for hot plasma diagnostics
Plasma control
Plasma diagnostics - interferometry, spectroscopy and imaging
Projectiles
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Summary:A CO2 Dispersion Interferometer (DI) system on the Experimental Advanced Superconducting Tokamak (EAST) was successfully operated, providing plasma electron density measurements. The DI system utilizes a continuous-wave 9.3 μm CO2 laser source to measure line-averaged electron densities. This offers significant advantages, including the ability to minimize fringe jumps and insensitivity to mechanical vibrations. These characteristics are well-suited for future high-density, long-pulse plasma discharges. The DI system provides a real-time density feedback signal to the plasma control system for routine density control during long-pulse operation. Experiments with EAST demonstrated good agreement between the density obtained by the DI system and the preset densities. The DI system also exhibited stability during long-pulse discharge. Moreover, the DI system was stable during rapid density changes and high-density pellet injections. In shot No. 120594, the DI system exhibited stable density feedback during continuous projectile injection lasting over 50 seconds; the line-averaged electron density is approximately 4×1019 m-3. In contrast to the long-wavelength source interferometer, which may deflect light from the detector owing to excessive refraction angles in larger density-gradient discharges, the DI ensured accurate density measurements. The DI system on EAST is dependable for accurately measuring the electron density.
ISSN:1748-0221
DOI:10.1088/1748-0221/19/04/C04021