The new concept of light nuclear beams instead of proton beams for ADS is substantiated. The influence of the target structure on the energy efficiency of 0.5-4 GeV proton beams and 0.25 – 0.5 AGeV light ion beams is studied. The target consists of rods with different composition (metal, oxide, carbide) and different levels of enrichment in order to implement the target with a criticality coefficient of 0.96 -0.97, which ensures safe operation. The cooling with different metals (lead, lead-bismuth eutectic - LBE, and sodium) is compared. The use of converters from very light materials (lithium, beryllium, carbon) and their influence on the neutron spectrum and energy released are analysed.