The use of a low contrast nanosecond laser pulse with a relatively low intensity (3 × 1016 W cm−2) allowed the enhancing of the yield of induced nuclear reactions in advanced solid targets. In particular the 'ultraclean' proton–boron fusion reaction, producing energetic alpha particles without neutron generation, was chosen. A spatially well-defined layer of boron dopants in a hydrogen-enriched silicon substrate was used as a target. A combination of the specific target composition and the laser pulse temporal shape allowed the enhancing of the yield of alpha particles up to 109 per steradian. This result can be ascribed to the interaction of the long-laser pre-pulse with the target and to the optimal target geometry and composition.