Cold pulse propagation in a reversed-field pinch

The cold pulse propagation is a powerful tool for the study of heat transport and the determination of perturbative electron heat diffusivity χeCP. In this paper the experimental study of cold pulses generated by pellet injection in a reversed-field pinch device is described. The most common phenomenology is an inward cold pulse propagation, from the edge to the core; however, we will describe that outward propagation can occur if the pellet ablates up to the plasma centre. A model to simulate the dynamics of the pulse (i.e. the relation between the arrival time of the pulse and its radial position) has been developed. With this model it is possible to explain the cold pulse phenomenologies as well as to estimate χeCP in the plasma core. The heat diffusivity in standard and enhanced confinement plasmas has been determined and compared; in standard regimes χeCP is three times larger than in enhanced confinement regimes. Finally, it has been possible to confirm a scaling between diffusivity and magnetic stochasticity