In recent years, it has been found that the application of local heat sources in a fusion plasma can influence the shape of the density profile. This shows that a coupling between heat and particle transport exists, which is taken into account in transport models by introducing off-diagonal transport coefficients. In existing studies, the focus of analysis is mostly on the density profile that occurs after a sufficiently long settling time after altering the heating power level. In this paper, the transient behaviour of temperature and density in response to steps in the applied heating power is analysed, which leads to the observation of hysteresis loops in the local density–temperature diagram. Based on numerical transport simulations, it is shown that the occurrence of hysteresis curves can be reproduced on the basis of today's physics understanding, where the shape of the curve provides additional information on the transport coefficients and their interdependences.
Interpretation of heat and density pulse measurements in JET in terms of coupled transport