A very high flux of hydrogen atoms with energies in the eV range has been obtained by using a thermal plasma source and by optimization of the nozzle exit geometry. It proves that the flux of hydrogen atoms emerging from a cascaded arc plasma source depends strongly on the geometry of the nozzle. By decreasing the nozzle length by a factor 2, the atomic hydrogen flux is increased by a factor of 13, and a further increase of a factor of 2.5 can be obtained by increasing the nozzle diameter. The resulting atomic hydrogen flux is 1.2×1021 s–1, corresponding to a dissociation degree of over 30%. It is argued that the main loss channel for atomic hydrogen is surface recombination, and that by using nozzle geometries that reduce the surface loss, the atomic flux is increased.