To obtain the maximum neutralised fraction in the extracted beam requires a higher line density in the neutraliser than calculated from the cross sections. No evidence is found to support the hypothesis that the heating of the neutraliser gas by the beam is the main source for the observed reduced neutralisation efficiency. The theoretical maximum in the neutral fraction can be achieved at higher gas flows which are however associated with higher losses through charge changing collisions. Implantation and re-emission of gas in the neutraliser walls appears to have a strong influence onto the particle density of the neutraliser. There is clear evidence of space charge blow up in the ion beam at low densities, which complicates the interpretation of the measurements. The present deflection system on TB is found suitable for neutralisation measurements, however energy reflection has to be taken into account and the system is not sensitive to losses in the magnet.