Abstract. A neutron diffraction crystal spectrometer with a resolution of 13 microseconds per meter and monochromatic beam intensity up to 10(4)n/cm(2)=sec in the range 0.012-0.400 ev has been constructed for study of the activation cross section of Be7 as a function of energy in the thermal region. First preliminary results using ZnS(Ag) as a detector suggest the possibility of a resonance for the Be7(n,p)Li7 reaction in the region of 0.025-0.050 ev.