Integrated neutron power spectra in the jet frame, for different values of the top of the acceleration (and in this case also emission) region, z_t = z_max. Blue stars indicate the value of P_n evaluated at the maximum neutron energy at z_t = z_max, i.e. the minimum value of along the jet for each model (cf. Fig. 5). In all the cases E_min = 5mc². The top (bottom) panel corresponds to a magnetic index m = 1.9 (1.5). The remaining parameters are those of Table 1.