HIGH INTENSITY CYCLOTRONS FOR RADIOISOTOPE PRODUCTION or THE COMEBACK OF THE POSITIVE IONS

High current cyclotrons are needed for the production of radioisotopes for nuclear medicine or for radiotherapy. Another application of high current cyclotrons is the production of 99mTc, either directly or as a fission product in a cyclotron-driven subcritical neutron source. The first cyclotrons for radioisotope production were classical, positive ions accelerators with E.S.D. extraction. The extracted beam intensity was limited to 100 IlA or less. Internal targets were used when higher currents were needed. The TCC model CP 42 was the first to introduce negative ions extraction, but still used an internal source. In 1987, IBA introduced the CYCLONE 30, featuring an innovative magnet design and an external ion source. Currents for such machines escalated over time to more than 1 mA extracted, with 2 or 3 mA in view. But, for very high intensities, positive ion acceleration still presents significant advantages, as illustrated by the CYCLONE 18+, operating daily at 2 mA continuously on an internal target. We describe a new method for the extraction of positive ions from a cyclotron without the need of a deflector or a similar device.