  We calculate the temperature and magnetic field distributions in a bulk
superconductor during the process of pulsed-field magnetic activation. The
calculations are based on the heat diffusion equation with account of the heat
produced by flux motion, and the critical state model with temperature
dependent critical current density. For a given activation time the total
amount of trapped flux is maximum for an optimal value B_opt of the maximal
applied field. We analyze how B_opt and the trapped flux depend on the material
parameters and the field ramp rate.
