This report presents the design and testing of an external target system for clinical‐scale production of 211At on the Scanditronix MC‐50 cyclotron at the University of Washington Medical Center. While other 211At production sites have typically employed an internal target, an external target setup was deemed necessary at our facility since the cyclotron's main application is for cancer patient treatment via fast neutron therapy. The challenge was that previous external 211At targets demonstrated reduced yields when compared to internal target systems. The target developed in this study has been used in more than 100 irradiations. From those irradiations 211At saturated yields of 181 ± 16 MBq/μA and 241 ± 17 MBq/μA at 28.0 and 29.0 MeV, respectively, were obtained. Importantly, consistent yields were observed over the 25–60 μA range of irradiation currents evaluated. With a recent production in excess of 4 GBq 211At for a 29.0 MeV, 58 μA, 4‐hour irradiation, this external target system has demonstrated its potential for producing clinically relevant quantities of 211At.

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The implementation of recent ICRP recommendations regarding the reduction of personnel radiation doses has necessitated some drastic changes in the philosophy and method of operation for several commercial cyclotron facilities. In previous years it was not uncommon for some operations personnel to receive 20-50 mSv/year due to the high radiation fields and operating schedule of some of these cyclotron facilities. The new limit commonly being adopted is 20 mSv/year and this has resulted in many of these facilities switching to more stringent operating routines e.g., scheduled preventative programs schedules, longer cooldown periods for repairs, more conservative beam current levels, and significant upgrades to cyclotron and targetry components. At the Nordion/TRIUMF facilities in Vancouver, Canada the recent upgrade of cyclotrons resulting in significantly higher operating beam currents has made the personnel radiation dose issue even more prominent. By a prudent choice of improved shielding schemes, carefully planned preventative maintenance, improvements to the cyclotron and the targetry hardware these problems have been managed such that individual personnel radiation doses below 10 mSv/year are achieved without compromising production.