Dynamic Stark spectroscopic measurements of microwave electric fields inside the plasma near a high-power antenna
C. C. Klepper, R. C. Isler, J. Hillairet, E. H. Martin, L. Colas, A. Ekedahl, M. Goniche, J. H. Harris, D. L. Hillis, S. Panayotis, B. Pegourié, Ph. Lotte, G. Colledani, V. Martin, and Tore Supra Lower Hybrid Systems Technical Team
Accepted
Fully dynamic Stark effect visible spectroscopy was used for the first time to directly measure the local RF electric field in the boundary plasma near a high-power antenna in high-performance, magnetically confined, fusion energy experiment. The measurement was performed in the superconducting tokamak Tore Supra, in the near-field of a 1-3 MW, lower-hybrid, 3.7 GHz wave-launch antenna, and combined with modeling of neutral atom transport to estimate the local RF electric field amplitude (as low as 1-2 kV/cm) and direction in this region. The measurement was then shown to be consistent with the predicted values from a 2D full-wave propagation model. Notably the measurement confirmed that the electric field direction deviates substantially from the direction in which it is launched by the waveguides as it penetrates only a few cm radially inward into the plasma from the waveguides, consistent with the model.