Up-Down and In-Out Asymmetry Monitoring Based on Broadband Radiation Detectors

Understanding the origin of asymmetries, either in plasma flows reaching the divertor region or in plasma emissivity from the confined volume, is a question of great interest in magnetic confined plasma research.In the TJ-II stellarator, a set of bolometer systems distributed around the vacuum chamber has been installed to monitor up-down and in-out radiation asymmetries that are observed in transitions to different confinement regimes. Although plasma emissivity is a complex magnitude, a comparison of signals from twin detectors placed at selected positions may be of help to distinguish between the different causes of asymmetry. Moreover, this is a nonperturbing method that is especially appropriate when plasma wall clearance is small.