ION-SOURCE WITH COMBINED CATHODE AND TRANSFER LINE HEATING

The plasma-discharge ion-source concept used in connection with the high temperature thick targets at the CERN-ISOLDE facility is described. Derived from the construction of the tubular surface ionizer, the same current which heats the transfer line between the target and the ion source is also used to heat the disc-shaped cathode. This construction has the advantage that the less volatile nuclear reaction products are transferred to the center of the source by diffusion along a rising temperature gradient, so that adsorption losses on the walls are minimized. The design, which exists in several versions dependent on the element to be ionized and the coupling between the target and ion source, is discussed and examples of the measured efficiencies are given.