Mandrillon, J. Abs, M. Cailliau, P. Cosson, O. Deprez, S. Donzel, X. Goosse, G. Jongen, Y. Kleeven, W.J.G.M. Koffel, L.C.L. Maunoury, L. Nuttens, V. Otu, Y. Paradis, Y. Velten, Ph. JACoW Publishing Geneva, Switzerland 2673-5482 978-3-95450-212-7 10.18429/JACoW-CYCLOTRONS2022-THBI01 English 264-268 cyclotron extraction proton resonance hadron Contribution to a conference proceedings 2023 2023-10 https://doi.org/10.18429/JACoW-CYCLOTRONS2022-THBI01 https://jacow.org/cyclotrons2022/papers/thbi01.pdf C400 is an isochronous cyclotron for cancer therapy delivering high dose rates of alphas to carbons at 400 MeV/amu extracted by electrostatic deflector and protons at 260 MeV extracted by stripping of molecular hydrogen. IBA started to pre-design the system more than 13 years ago in collaboration with JINR. The responsibility for the development of C400 has meanwhile been taken over by the French company Normandy Hadontherapy (NHa). However, the study and design work continued with a very strong involvement of IBA for the past 3 years, from concept on paper to reality. We will describe the most innovative concepts and technical solutions on the accelerator from source to extraction and show the construction progress.