A method for creating a first data set for modifying an irradiation plan parameter data set used for controlling an irradiation system for irradiating a target volume in an irradiation volume using an ion beam includes defining a sensitive volume within the biological material to be irradiated, determining a fluence distribution of the ion beam, determining a microscopic dose distribution of the ion beam, determining, from the microscopic dose distribution of the ion beam, a spatial microscopic damage distribution of the ion beam, determining an expected value for a number of correlated damage events in a sub-micrometer range in the sensitive volume from the spatial microscopic damage distribution of the ion beam in the sensitive volume, determining the effect of the ion beam on the biological material, and storing data that indicate the effect of the ion beam on the material.
