Observation and empirical modelling of the anomalous particle pinch in TCV

Moderately peaked electron density profiles are observed in virtually all plasma conditions in TCV. The existence of an anomalous pinch is unambiguously demonstrated by the observation of peaked density profiles in stationary, fully relaxed, fully current driven electron cyclotron current drive (ECCD) discharges with V-loop = 0. The behaviour of the density profiles from a database of 300 Ohmic L- and H-mode, as well as electron cyclotron heating and ECCD discharges, is compared to predictions of models based on the Ware pinch, the curvature pinch and anomalous thermodiffusion. Best overall agreement throughout the database is obtained with models combining an anomalous pinch mechanism, such as the curvature pinch, with the Ware pinch.