In a collaboration with CEA Cadarache, IPP is presently developing an rf source, in which the production of negative ions(H−/D−)is being investigated. It utilizes PINI-size rf sources with an external antenna and for the first step a small size extraction system with 48 cm2net extraction area. First results from BATMAN (BavarianT_estMachineforN_egativeIons) show (without Cs) a linear dependence of the negative ion yield with rf power, without any sign of saturation. At elevated pressure (1.6 Pa) a current density of 4.5 mA/cm2H−(without Cs) has been found so far. At medium pressure (0.6 Pa) the current density is lower by approx. a factor of 5, but preliminary results with Cesium injection show a relative increase by almost the same factor in this pressure range. Langmuir probe measurements indicate an electron temperatureTe>2&hthinsp;eVclose to the plasma grid with a moderate magnetic filter (700 Gcm). Attempts to improve the performance by using different magnetic configurations and different wall materials are under way. ©1998 American Institute of Physics.