High energy beams of high ion currents from a Tandem accelerator are a common requirement in nuclear physics, materials science and Accelerator Mass Spectrometry (AMS) research. In many cases, molecular beams are chosen from the ion source to achieve a high ion source yield for the negative ions, or, as for AMS, to suppress isobaric interference. For this reason we have studied the use of consecutive stripper foils, double stripping, to increase the ion yield in conjunction with increased energy of injected molecular beams through a Tandem accelerator. By this method we could achieve a shift in the yield towards higher charge states.