3rd and 4th generation ECRIS:: Some possible scenarios

Since the end of '70s the Electron Cyclotron Resonance ion sources (ECRIS) allowed to increase both the energy and intensity of the beams available from different types of accelerators; perspectives for the future are still optimistic. It is commonly agreed that only some ECRIS parameters have been fully exploited, whether some others are still not efficiently used, or not understood. The developments in the last 20 years have followed the so called Standard Model and the availability of higher frequency generators and higher field magnets have permitted relevant increase; the use of Nb3Sn may extend the range. The availability of new schemes of microwave coupling to plasma is promising, and the focusing of the electromagnetic wave towards the chamber axis may improve the density of warm electron population. The paper will also describe some critical point of the 3(rd) generation ECRIS (including technological troubles and limits) and the scenario for future 4(th) generation ECRIS, operating at f =56-75GHz, to be built in 2010s.