An In-Situ Calibration System For The Motional Stark Effect Diagnostic On ITER

The standard technique for measuring internal magnetic fields in fusion plasma experiments, the motional Stark effect diagnostic, relies on the analysis of visible light emit­ted from hydrogen beams in the plasma. However, in a fusion-relevant device with a large neutron ¿ux, a labyrinth of mirrors is required to transmit the light through an effective radiation shield. Any plasma-facing mirror would suffer erosion and deposition from plasma exposure, with adverse effects on the transmitted light. These effects not only could be significant but also could vary during the experiment, de­stroying the ability of the diagnostic to determine the magnetic field. This project will develop a comprehensive in situ calibration system for the motional Stark effect diagnostic in a burning plasma. In Phase I, calculations were performed, proof-of-principle laboratory tests were conducted, and innovative designs were developed for the necessary hardware. In Phase II, the hardware will be built and qualified in a plasma en­vironment, and the calibration technique will be performed during plasma exposure of a mirror. Commercial Applications and other Benefits as described by the awardee: This technology would provide substantial benefits to future magnetic fu­sion plasma experiments, including ITER, which will require accurate diagnostics of the internal magnetic field