Ion microbeams have emerged as a powerful tool in several domains of radiation biology. They have been used, for example, in the evaluation of environmental and occupational risks of exposure to low doses of ionizing radiation, or the study of temporal evolution of DNA damage and repair after irradiation of targeted (sub)cellular components, in cells or multicellular organisms. This paper reports the development and commissioning of the IRSN’s MIRCOM facility, constituted by a microbeam line and irradiation station, designed for targeted irradiation of living biological samples with a focused ion microbeam extracted in air. This equipment is able to provide protons, alpha particles, and heavier ions such as B, C, O, with energies up to a few MeV. The performances of the microbeam have been assessed, in a first step, with 4 MeV protons. The beam spot size has been evaluated on CR39 track detectors and living cells at 2.2 ± 0.3 µm, and the targeting accuracy of the system has been measured using online time-lapse imaging at 2.1 ± 0.7 µm. The monitoring of the number of ions hitting the target can be carried out either by defining an appropriate beam opening time, thanks to a good beam stability and with regular beam monitoring between samples, or by placing thin ion detectors, currently under characterization, on the path of the beam for the lower numbers of ions. Future work will aim at improving the versatility of the MIRCOM facility, to be able to irradiate a wider variety of biological samples, from cellular to multicellular organisms.< Leer menos