The nuclear reactions 25Mg(, n)28Si, 26Mg(, n)29Si and 18O(, n)21Ne are investigated in the astrophysically interesting energy region from E = 1000 keV to E = 2450 keV. The experiments were performed at the Nuclear Structure Laboratory of the University of Notre Dame (USA) with the Van-de-Graaff accelerator KN. Solid state targets with evaporated magnesium or anodized oxygen were bombarded with -particles and the released neutrons detected. For the detection of the released neutrons, computational simulations were used to construct a neutron detector based on 3He counters. Because of the...