Matlocha, T. JACoW Publishing Geneva, Switzerland 978-3-95450-205-9 10.18429/JACoW-Cyclotrons2019-TUP014 English 185-188 TUP014 extraction cyclotron septum simulation proton Contribution to a conference proceedings 2020 2020-06 https://doi.org/10.18429/JACoW-Cyclotrons2019-TUP014 http://jacow.org/cyclotrons2019/papers/tup014.pdf NPI Řež U-120M multi-particle variable energy cyclotron system for positive ions extraction consists of three electrostatic deflectors, one active magnetic channel and an electromagnetic bump exciter. The deflectors transmission ratio for deuterons, alpha particles and Helium 3 ions is rather low, usually about 10%, for protons it is far below 5%. Based on an experience from other cyclotron laboratories, the general concept of the extraction system has been modified and the last two electrostatic deflectors were replaced with two magnetic channels. In the early stage of the upgrade, simulations were performed for protons at 28 MeV and Helium 3 ions at 44 MeV with and without the magnetic bump exciter. The extraction efficiency and beam losses along the extraction path are evaluated. The presented modified extraction system simulations suggest promising results. The total transmission ratio of the deflecting system has increased significantly, allowing work to continue and expect a positive final result.