[en] Future CERN programs for the large hadron collider (LHC) and the isotope online separator (ISOLDE) require increasing the beam intensity and brightness from the proton synchrotron booster (PSB). This could be achieved by charge-exchange injection with phase-space painting into the PSB acceptance from a higher energy H^- linac. A new injector will require a high performance, high reliability, negative hydrogen-ion source. This article will present the results achieved so far with a prototype microwave-driven source operated with three different magnetic structures (multicusp, solenoidal, and a combination of both). The experiments were carried out with different mixing gases, different chamber inserts, and under a wide range of operational conditions