Multi-device study of electron temperature profile evolution and plasma disruptions through Disruption Event Characterization and Forecasting (DECAF) analysis

Rapid plasma dynamics providing early disruption forecasting such as the presence of MHD modes [1], magnetic islands [2] and sudden changes on the magnetic topology of the plasma [3] can all be inferred from the evolution of the electron temperature profile. In particular, electron temperature collapses caused by a change in the magnetic topology are the signature of nonlinear events such as flux surface tearing, observed due to the sudden thermal transport that follows the opening of the field lines. Such tearing can result on a change in the plasma state due to NTM seeding, H-L back transition or influx of impurities due to plasma touching the walls, often leading to a plasma disruption. In this work, a general framework to identify and characterize electron temperature collapses is outlined and implemented in the Disruption Event Characterization and Forecasting [4] code, allowing for multi-year, multi-device analysis of such thermal collapse events and their precursors. Of critical importance is the categorization of the electron temperature collapse and its relation to key physics events, which can in future machines trigger disruption control and mitigation schemes. Finally, it is shown that the soft gradients in evolution of the electron temperature profile, mode activity and the general plasma state can provide proximity warnings to the observation of the electron temperature collapse, providing an opportunity for disruption avoidance.

[1] V. Igochine etal 2017 Nucl.Fusion 57 036015

[2] Y S Park, Plasma Phys. Control. Fusion 48 (2006) 1447–1454

[3] G Bustos-Ramirez, iFPC 3^rd International Fusion and Plasma Conference (Seoul, Korea, June 2024).

[4] S.A. Sabbagh, et al., Phys. Plasmas 30, 032506 (2023); https://doi.org/10.1063/5.0133825