A novel ion beam radiation therapy apparatus employing pulsed high magnetic field coils for transporting the ion beam has been proposed. In this paper a new pulsed current converter topology is introduced, which can be used as a pulsed power supply for the therapy apparatus. Thyristors are selected as the semiconductors used in the pulsed current converter. Since the planned operating point is outside of the typical range of the semiconductors, research has been done to predict their behavior during turn-off (the most critical phase of the pulse). A behavioral model has been derived and experimentally parametrized to predict the turn-off behavior and to optimize snubber design.