Efficiency and transient time studies of an electron cyclotron resonance ion source for radioactive ion beam production at ISAC/TRIUMF

A 2.45 GHz electron cyclotron resonance (ECR) ion source with a single mode resonator is being developed to produce high efficient single charged ion beams from exiguous gaseous elements. The source is intended to produce short and long half-life radioactive ion beams as well as stable ion beams for low and high energy experiments at ISAC [J. M. Poutissou, Proceedings of the ISAC Workshop (1994)]. It is obvious that for the radioactive ion beam production, the gas and ion transient time and the overall ionization efficiency are the most important parameters. The transient time is measured using ultrafast peizoelectric gas valve which could operate up to a frequency of 2 kHz. A unique feature of the source is that the plasma chamber is considerably smaller (similar to 170 times) than its resonance cavity in order to minimize the transient time. Quartz tubes with various diameters (5-20 mm) and 80 mm long are tested as the plasma chamber and the results are discussed. The effect of the transfer tube length, which links the target and the ion source on the transient time is also described. An axially symmetric five electrode extraction system containing three multiaperture electrodes was used to extract the beam. The source, including ECR coils and extraction system is placed in the middle of a 60 cmx60 cmx90 cm vacuum box to simulate the ISAC target module conditions. The preliminary results of the molecular and ion transient time studies, beam efficiency studies are also presented in this article. (C) 2000 American Institute of Physics. [S0034-6748(00)53602-8].