A detection signal generated in response to incident ions accelerated at temporally-irregular intervals having an average repetition rate greater than a reference repetition rate represents detection events each having an event time and an intensity. For each detection event, respective allowed TOFs between the event time and the transient times are calculated. Using respective initial probabilities, initial apportionments of the intensity of each detection event among the allowed TOFs linked thereto are determined. For each allowed TOF, the intensity apportionments thereto are accumulated to generate an intensity accumulation linked thereto. For each detection event, respective revised probabilities are iteratively determined using the intensity accumulations linked to the allowed TOFs linked thereto, and the respective intensity is iteratively reapportioned among the allowed TOFs linked thereto using the revised probabilities to transform the detection signal to a time-of-flight spectrum.