The medical cyclotron at the Bern University Hospital (Inselspital) is used for both routine 18 F production for Positron Emission Tomography (PET) and multidisciplinary research. It provides proton beams of variable intensity at a nominal fixed energy of 18 MeV. Several scientific activities, such as the measurement of nuclear reaction cross-sections or the production of non-conventional radioisotopes for medical applications, require a precise knowledge of the energy of the beam extracted from the accelerator. For this purpose, a study of the beam energy was performed as a function of cyclotron operational parameters, such as the magnetic field in the dipole magnet or the position of the extraction foil. The beam energy was measured at the end of the 6 m long Beam Transfer Line (BTL) by deflecting the accelerated protons by means of a dipole electromagnet and by assessing the deflection angle with a beam profile detector.

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The production of theranostic radionuclides using solid targets is challenging and requires an accurate knowledge of the production crosssections as well as the energy, positioning and focusing of the beam. A research program is ongoing at the 18 MeV Bern medical cyclotron, equipped with a Solid Target Station (STS) and a 6 m Beam Transfer Line (BTL) ending in a separate bunker with independent access. A novel target coin was designed and built to irradiate compressed powder pellets, together with a compact focalization system to optimize the irradiation procedure. Furthermore, methods were developed to measure the beam energy, the production cross-sections and the EoB-activity.

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 43Sc and 44Sc, 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.

A novel three-dimensional non-destructive beam monitor named π3 was conceived, realized and tested. It is based on a thin aluminum foil coated with P47 scintillating material mounted on a support, together with a miniaturized CCD camera, both moving along the beam axis. This detector allows reconstructing of the beam distribution along the beam path, providing either an on-line video or a graphical reconstruction of the beam envelope in 3D. The π3 detector is a general-purpose instrument suitable for any ion accelerator facility. As it is constructed with non-magnetic materials, it can be used to investigate the behavior of the beam inside beam optics components such as magnets. In this paper, we report the development of the first prototype of the π3 detector, its associated software and the results of the beam tests performed at the Bern medical cyclotron laboratory.