Kleeven, W.J.G.M. Forton, E. JACoW Publishing Geneva, Switzerland 978-3-95450-205-9 10.18429/JACoW-Cyclotrons2019-THD03 English 330-333 THD03 extraction cyclotron ion-source simulation site Contribution to a conference proceedings 2020 2020-06 https://doi.org/10.18429/JACoW-Cyclotrons2019-THD03 http://jacow.org/cyclotrons2019/papers/thd03.pdf A study is made for an improved concept of self-extraction in low and medium energy cyclotrons to be used for production of medical isotopes. The prototype of the self-extracting cyclotron was realized around the year 2001*. From this machine, currents higher than 1 mA were extracted and transported to a Pd-10³ production target. However, at the higher intensities, the extraction efficiency was dropping to about 70-75%, and the extracted emittance was rather poor, leading to additional losses in the beamline. Several improvements of the original concept are proposed: i) the beam coherent oscillation (as needed for good extraction) is no longer generated with harmonic coils, but is obtained from a significant off-centring of the ion source, ii) the cyclotron magnet has perfect 2-fold symmetry, allowing the placement of two internal sources and dual extraction on two opposite hill sectors, iii) a substantial improvement of the magnetic profile of the hill sectors. Simulations show an extraction efficiency up to almost 95% and emittances at least a factor 3 lower as compared to the original design. The new magnetic design is shown, and results of beam simulation are discussed.