A compact Ge-BGO coincidence array for ultra-sensitive in-beam gamma spectroscopy

Ultra-weak resonances in nuclear reactions impose a challenge on experimentalists. The present work describes the setup used in the first direct measurement of extremely weak low energy resonances of the 18O(α, γ)22Ne reaction. A Clover HPGe detector in coincidence with specified energy windows in BGO counters covering a large solid angle, and combined with large plastic veto counters led to a significantly improved sensitivity, thus allowing for the clear identification of specific γ-transitions. Different modes of operation have been tested for optimizing the final experimental setup.