ITER Edge Thomson Scattering

Abstract

Many of ITER’s performance limiting mechanisms are expected to exist and interact at the plasma edge. The H-mode edge pedestal parameters are high leverage variables of models used for predicting ITER’s success, in measures ranging from core reactivity to divertor erosion. For example, the pedestal temperature is critical in determining the L-H transition. According to many transport models, once H-mode is reached, the H-factor and Q are strongly related to the pedestal pressure. Several classes of ELM instabilities are sensitive to the edge pressure profile shape and also affect performance. The ITER divertor scenario counts on impurity radiation from the plasma edge to reduce power flow to the divertor plates, a mechanism that also affects the edge pedestal region. It is therefore reasonable to expect that, during ITER operation, the edge T_e and n_e profiles are likely to become key operational indicators, and ideally, they would be available for use in feedback control for discharge optimization.