A new fast two-color interferometer at Alcator C-Mod for turbulence measurements and comparison with phase contrast imaging

作者：Kasten C P^*; White A E; Irby J H

来源：Physics of Plasmas, 2014, 21(4): 042305.

DOI：10.1063/1.4871392

Accurately predicting the turbulent transport properties of magnetically confined plasmas is a major challenge of fusion energy research. Validation of transport models is typically done by applying so-called "synthetic diagnostics" to the output of nonlinear gyrokinetic simulations, and the results are compared to experimental data. As part of the validation process, comparing two independent turbulence measurements to each other provides the opportunity to test the synthetic diagnostics themselves; a step which is rarely possible due to limited availability of redundant fluctuation measurements on magnetic confinement experiments. At Alcator C-Mod, phase-contrast imaging (PCI) is a commonly used turbulence diagnostic. PCI measures line-integrated electron density fluctuations with high sensitivity and wavenumber resolution (1.6 cm(-1) less than or similar to vertical bar k(R)vertical bar less than or similar to 11 cm(-1)). A new fast two-color interferometry (FTCI) diagnostic on the Alcator C-Mod tokamak measures long-wavelength (vertical bar k(R)vertical bar less than or similar to 3.0 cm(-1)) line-integrated electron density fluctuations. Measurements of coherent and broadband fluctuations made by PCI and FTCI are compared here for the first time. Good quantitative agreement is found between the two measurements. This provides experimental validation of the low-wavenumber region of the PCI calibration, and also helps validate the low-wavenumber portions of the synthetic PCI diagnostic that has been used in gyrokinetic model validation work in the past. We discuss possibilities to upgrade FTCI, so that a similar comparison could be done at higher wavenumbers in the future.

• 出版日期2014-4