Pellet injection is used for fuelling and controlling discharges in tokamaks,
and it is foreseen in ITER. During pellet injection, a movement of the ablated
material towards the low-field side (or outward major radius direction) occurs
because of the inhomogeneity of the magnetic field. Due to the complexity of
the theoretical models, computer codes developed to simulate the cross-field
drift are computationally expensive. Here, we present a one-dimensional
semi-analytical model for the radial displacement of ablated material after
pellet injection, taking into account both the Alfv\'en and ohmic currents
which short-circuit the charge separation creating the drift. The model is
suitable for rapid calculation of the radial drift displacement, and can be
useful for e.g. modelling of disruption mitigation via pellet injection.Comment: 22 pages, 4 figures. Submitted to Journal of Plasma Physic