An Active Irradiation System with Automatic Beam Positioning and Focusing for a Medical Cyclotron

• Main Authors: Philipp Daniel Häffner, Carolina Belver-Aguilar, Pierluigi Casolaro, Gaia Dellepiane, Paola Scampoli, Saverio Braccini
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Applied Sciences
• Subjects: particle accelerator; medical cyclotron; automatic irradiation system; beam diagnostics; solid targets; medical radioisotope production
• Online Access: https://www.mdpi.com/2076-3417/11/6/2452

A novel active focusing system was developed for enhancing the irradiation performance of the 18 MeV medical cyclotron in operation at the Bern University Hospital in view of the production of non-conventional medical radioisotopes using solid targets. In several cases, such as the production of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>43</mn></msup></semantics></math></inline-formula>Sc and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>44</mn></msup></semantics></math></inline-formula>Sc, the beam has to be kept stable within a very small target of about 5 mm diameter. For this purpose, we conceived and realized an apparatus based on a compact focusing and steering magnet system followed by a two-dimensional beam monitoring detector and a specific feedback software that drives the magnet to optimize the beam for a given irradiation set-up. We report on the design, realization and validation beam tests performed using the research beam transfer line of the Bern cyclotron. We demonstrated that the beam spot can be kept on target thanks to the fact that the system automatically reacts to perturbations. Compactness is one of the key features of this system, allowing its use in accelerator facilities with limited space, such as medical cyclotrons for radioisotope production.