The Self-extracting Cyclotron

At IBA a compact 14 MeV H+ cyclotron has been constructed. A special feature of this cyclotron is that there is no electrical deflector installed, i.e. the beam is selfextracted. The goal is to obtain high beam currents with good extraction efficiency without the need of single turn extraction. This is achieved with two ingredients: i) a special shaping of the magnetic field, showing a very steep fall-off near the outer radius of the pole and ii) the creation of a large turn-separation on the last turn. The pole gap has a quasi-elliptical shape, allowing for the steep fall-off of the magnetic field by the machining of a groove in one of the poles at a radius where the gap is small. The large turn separation is obtained by either the use of harmonic coils or by permanent magnet field bumps placed in two opposite valleys. Both methods have been tested and give good results with an extraction efficiency of 80 %. The concept and layout of the machine is explained. The status of the project is outlined. First results of beam tests are presented. The cyclotron is intended for medical isotope production at multi-mAbeam intensity.