A methodology for TIE detection and tracking for JET’s experimental cameras

Abstract

Transient Impurity Events (TIEs), also referred as UFOs, are small particles found in nuclear fusion devices formed as by-products of plasma operation. TIEs have been a main focus of study due to their effects on the behaviour of the plasma. Here, we evaluate the statistical effects of TIEs on disruptions in JET using cameras, often underutilised diagnostics in plasma studies. First, in a dataset of 876 discharges, it was found that in 38.4% of pulses with TIEs, a disruption was detected. Out of these, 11.9% occurred in a critical time interval that indicates that the TIE might have caused the disruption. 24.1% of the TIEs found were originated right after one. A review of the TIE composition, position and speed has also been performed in a reduced dataset of 77 pulses, resulting in the dominant presence of W and Ti TIEs over the rest (33.7% and 29.9%), most notably from the divertor and the Upper Dump Plate Tiles (UDPT) (18.2% and 27.3%, respectively). The analysis of TIE speed, however, did not yield further insights into their disruptive behaviour.