A full aperture backscatter station (FABS) target diagnostic has been activated on the first four beams of the National Ignition Facility. FABS measures both stimulated Brillouin scattering and stimulated Raman scattering with a suite of measurement instruments. Digital cameras and spectrometers record spectrally resolved energy for both P and S polarized light. Streaked spectrometers measure the spectral and temporal behavior of the backscattered light. Calorimeters and fast photodetectors measure the integrated energy and temporal behavior of the light, respectively. This article provides an overview of the FABS measurement system and detailed descriptions of the diagnostic instruments and the optical path.
For the stabilization of neoclassical tearing mode (NTM), Electron Cyclotron Current Drive (ECCD) is used. The change of the EC control efficiency depends on EC modulation width and EC injection phase lag from the Opoint of magnetic island. In this work, NTM stabilization by ECCD is analyzed using 1.5-dimensional transport code TOTAL, in which the time variation of magnetic island is described by the modified Rutherford equation. NTM in ITER can be stabilized when the EC phase lag is smaller than 10% and the EC modulation width is around 20%, when the time-averaged EC current and power is fixed.
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