Mallory Smith

Scintillation Efficiency Measurement of Na Recoils in NaI(Tl) Below the DAMA/LIBRA Energy Threshold

The dark matter interpretation of the DAMA modulation signal depends on the NaI(Tl) scintillation efficiency of nuclear recoils. Previous measurements for Na recoils have large discrepancies, especially in the DAMA/LIBRA modulation energy region. We report a quenching effect measurement of Na recoils in NaI(Tl) from 3keV

Systematic Study Of (p,γ) Reactions On Ni Isotopes

_{\text{nr}}

Low-lying level structure of Cu 56 and its implications for the rp process

to 52keV

A measurement of the ionization efficiency of nuclear recoils in silicon

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Measurement of the 90,92Zr(p,γ)91,93Nb reactions for the nucleosynthesis of elements near A=90

, covering the whole DAMA/LIBRA energy region for light WIMP interpretations. By using a low-energy, pulsed neutron beam, a double time-of-flight technique, and pulse-shape discrimination methods, we obtained the most accurate measurement of this kind for NaI(Tl) to date. The results differ significantly from the DAMA reported values at low energies, but fall between the other previous measurements. We present the implications of the new quenching results for the dark matter interpretation of the DAMA modulation signal.

Measurement of the 58Ni(α, γ) 62Zn reaction and its astrophysical impact

A systematic study of the radiative proton capture reaction for all stable nickel isotopes is presented. The results were obtained using 2.0–6.0 MeV protons from the 11-MV tandem Van de Graaff accelerator at the University of Notre Dame. The γ rays were detected by the NSCL-SuN detector utilizing the γ -summing technique. The results are compared to a compilation of earlier measurements and discrepancies between the previous data are resolved. The experimental results are also compared to the theoretical predictions obtained using the NON-SMOKER and SMARAGD codes. Based on these comparisons an improved set of astrophysical reaction rates is proposed for the (p, γ) reactions on the stable nickel isotopes as well as for the 56 Ni(p, γ) 57 Cu reaction.

Measurement of the

The low-lying energy levels of proton-rich Cu56 have been extracted using in-beam γ-ray spectroscopy with the state-of-the-art γ-ray tracking array GRETINA in conjunction with the S800 spectrograph at the National Superconducting Cyclotron Laboratory at Michigan State University. Excited states in Cu56 serve as resonances in the Ni55(p,γ)Cu56 reaction, which is a part of the rp process in type-I x-ray bursts. To resolve existing ambiguities in the reaction Q value, a more localized isobaric multiplet mass equation (IMME) fit is used, resulting in Q=639±82 keV. We derive the first experimentally constrained thermonuclear reaction rate for Ni55(p,γ)Cu56. We find that, with this new rate, the rp process may bypass the Ni56 waiting point via the Ni55(p,γ) reaction for typical x-ray burst conditions with a branching of up to ∼40%. We also identify additional nuclear physics uncertainties that need to be addressed before drawing final conclusions about the rp-process reaction flow in the Ni56 region.

^{58}

We have measured the ionization efficiency of silicon nuclear recoils with kinetic energy between 1.8 and 20 keV . We bombarded a silicon-drift diode with a neutron beam to perform an elastic-scattering experiment. A broad-energy neutron spectrum was used and the nuclear recoil energy was reconstructed using a measurement of the time of flight and scattering angle of the scattered neutron. The overall trend of the results of this work is well described by the theory of Lindhard et al. above 4 keV of recoil energy. Below this energy, the presented data shows a deviation from the model. The data indicates a faster drop than the theory prediction at low energies.

Ni(

Cross section measurements of the reactions

\alpha

^{90, 92}