The report presents a five‑year research and design effort aimed at building a next‑generation accelerator‑based research infrastructure for ion‑beam cancer therapy and biomedical science in South‑East Europe. The facility, to be located at the SEEIIST site, will combine proven European ion‑therapy technology with innovative features that promise to surpass the performance of existing carbon‑ion centres. The design work builds on the experience of the PIMMS project, which was successfully implemented in the CNAO and MedAustron centres between 1996 and 2000, and on recent advances in accelerator science.
The technical core of the proposal is a synchrotron that can accelerate carbon ions to 5000 MeV, the energy required for treating deep‑seated, radioresistant tumours. The baseline layout follows the FODOF lattice used in PIMMS, employing 16 dipole magnets and two long, dispersion‑free straight sections that simplify injection, acceleration and extraction. The circumference of the ring is about 55 m, matching the size of current European facilities. Two alternative lattice concepts are under study. The first reduces the number of magnets, potentially lowering cost and simplifying operation while retaining the dispersion‑free sections. The second, a double‑bend achromat (DBA) design proposed by the University of Melbourne, uses only 12 dipoles and also achieves a 55‑m circumference, but with fewer quadrupoles, offering a more compact and cost‑effective solution.
A third, superconducting option is being pursued in partnership with the TERA Foundation and a consortium of European laboratories and industry partners. This design replaces conventional warm magnets with 90° canted cosine‑theta (CCT) superconducting dipoles operating at 3.5 T, and a 4 T gantry magnet of the same type. The CCT geometry allows nested alternating‑gradient quadrupoles (AG‑CCT) to be integrated into the same coil, reducing the overall footprint. The superconducting system will be built with a conventional NbTi conductor, with plans to evaluate Nb₃Sn and high‑temperature superconductor (HTS) options. Prototype magnets are scheduled for construction and testing by 2025 under the EU programmes I.FAST and HITRIplus, which also provide the financial support for the project.
Radiobiological modelling is a key component of the design. The report discusses the use of the local effect model (LEM) to predict relative biological effectiveness (RBE) across the Bragg peak, highlighting the importance of linear energy transfer (LET) and dose fractionation. The facility will be capable of delivering high‑precision spread‑out Bragg peaks (SOBPs) with flat dose distributions, as demonstrated in current centres such as NIRS, HIT and CNAO. The design also incorporates FLASH‑mode capabilities, which require ultra‑fast dose rates and are expected to reduce normal‑tissue toxicity.
The collaboration that underpins the project is broad and multinational. Key partners include the CNAO Foundation (Pavia, Italy), the Paul Scherrer Institute (Villigen, Switzerland), CERN (Geneva, Switzerland), the University of Aarhus (Denmark), the University of Heidelberg (Germany) and the TERA Foundation (Italy). The editorial board, led by Ugo Amaldi, Elena Benedetto, Panagiota Foka, Sandro Rossi and Maurizio Vretenar, coordinates the scientific and technical activities. The project is funded through EU research programmes, with additional support from national agencies in the participating countries. Over the five‑year period, the consortium will deliver a detailed technical design, prototype magnets, and a comprehensive assessment of the facility’s clinical and research capabilities, positioning the SEEIIST centre as a leading hub for ion‑beam therapy and biomedical research in South‑East Europe.