SELF-EXTRACTION IN A COMPACT HIGH-INTENSITY H CYCLOTRON AT IBA

At IBA a compact 14 MeV H cyclotron is under construction. A special feature of this cyclotron is that there is no electrical deflector installed, i.e. the beam is self-extracted. This is achieved by a special shaping of the magnetic field, which shows a very steep fall-off near the outer radius of the pole and at the same time a strong first harmonic component in the extraction region. The steep fall-off is obtained with a small quasi-elliptical pole gap and the machining of a groove in one of the poles. The strong first harmonic is obtained with permanent magnet field bumps placed in two opposite valleys. Results of Tosca simulations, field mapping and tracking are presented.