The method of the invention comprises the steps of: providing a reference ion beamlet determining in a phantom (60) a distribution of a linearly-superposable quantity representing a linearly-superposable effect induced by said reference ion beamlet approximating an ion beam (10) as a weighted superposition of ion beamlets (15), said weighted superposition comprising weight coefficients, at least one ion beamlet (15) being obtained by applying a roto-translation operation to said reference ion beamlet determining a roto-translated distribution of a linearly-superposable quantity by roto-translating said distribution of a linearly-superposable quantity with said roto-translation operation determining said physical and/or radiobiological quantities by performing a weighted superposition comprising said weight coefficients, and said roto-translated distribution of a linearly-superposable quantity.
