[en] Beam stability and reproducibility is of paramount importance in applications requiring precise control of implanted radiation dose, like in the case of hadron-therapy. The beam intensity over several weeks and months should be kept constant. Standard valves used usually in conjunction of ECR ion sources have the disadvantage of controlling the conductance, which can vary significantly with external conditions, like ambient temperature and inlet pressure of the gas. The use of flow-controllers is the natural way for avoiding these external constraints. In this contribution we present the results obtained using a new model of mass-flow controller in the Supernanogan source for production of C⁴⁺ and H³⁺ beams. The minimum flow with this system is 0.014 ml_n/min until 0.06 ml_n/min. Extremely stable beams (± 2.5%) without retuning the source over several weeks can be obtained. The reproducibility of the source tuning parameters can also be demonstrated. The paper is followed by the associated poster. (authors)