A water target with beam sweep for routine fluorine-18 production

Fluorine-18 (18F) production with 18O-enriched water targets is well established world-wide. Heat transfer is still a critical point, however, when high beam currents are used to increase the amount of radioactivity per batch within an adequate irradiation period. The technique of beam sweep formerly used in Hannover for all targets has been adapted for this water target again. A titanium target with a beam sweep of up to 3 cm in the horizontal plane was designed to keep the total amount of enriched water low (2.06 ml), to allow beam currents of 30 microA for 1 h on a daily schedule and thereby to extend maintenance periods to more than 6 months. The design had to take into account that the target must be mounted on a target ladder with five additional positions and that the beam is carried by a 5.50 m beam line from a variable energy, multi-particle cyclotron (mc35, Scanditronix) to the target. The target has been in use for more than 130 consecutive runs with beam currents of about 30 microA at a target pressure of up to 15 bar without any maintenance. The mean value of the recovered radioactivity has reached 91.9+/-7.7% of the theoretically expected value at the end of bombardment (EOB).