Resonance strengths in the 17,18O(p, α)14,15N reactions and background suppression underground: Commissioning of a new setup for charged-particle detection at LUNA

We report on measurements of resonance strengths and energies for the Ep = 151 and 193 keV resonances in the 18O(p,α)15N and 17O(p,α)14N reactions, respectively, obtained during commissioning of a new setup for alpha-particle detection studies at the LUNA underground laboratory. Our values, (Formula Presented.) meV, are in excellent agreement with those reported in the literature. New values of resonance energies are Ep =151.2±0.3keV and Ep =194.8±0.3keV, respectively, this latter with the highest precision to date. Comparative background measurements in silicon detectors overground and underground were also carried out, yielding up to a factor of 15 in background suppression at LUNA at energies around 200keV. This clearly demonstrates the usefulness of underground measurements in charged-particles experiments, especially at low detection energies.