[en] A post accelerator, primarily to provide beams of interest to nuclear astrophysics users, is included in the upgrading and expansion of the radioactive beam facility at TRIUMF. Singly charged ion beams, with A ≤ 30, delivered from the on line mass separator with an energy of 2 keV/u, will be accelerated in a stage linac consisting of an RFQ and a post-stripper drift-tube. As a consequence of the low charge-to-mass ratio of the ions, a low operating frequency for the RFQ is required to achieve adequate transverse focusing. CW operation is specified to preserve beam intensity. Because of its relatively high specific shunt impedance, mechanical stability, and the absence of vane voltage asymmetries in the end regions, the split-ring 4-rod RFQ structure has been chosen. Several cold models have been built to study three different types of split-ring RFQ structures. Specific shunt impedance and longitudinal field have been measured. A comparison of these measurements for various split-ring structures is presented. (author). 8 refs., 6 tabs., 5 figs