Novel technique for constraining r-process (n,γ) reaction rates. The r-process is responsible for producing nearly half of all the heavy elements. We seek to understand how the r-process works and in what astrophysical sites it occurs. Improving the physics input parameters in astrophysical models is paramount to answering these questions. A new experimental technique has been developed that constrains difficult to measure neutron capture cross sections for isotopes far from stability. This technique is called the β-Oslo method. A. Spyrou et al., Phys. Rev. Lett. 113 (2014) 232502 E. Poirier et al., Phys. Rev. C69 (2004)

First Application of the β-Oslo Method. Indirect Measurement of 75Ge(n,γ)76Ge β- (n,γ) 76Ga A, Z-1 75Ge A-1, Z γ 76Ge A, Z Detector: SuN with a small silicon surface barrier detector (SSBD) placed inside. Beam: Unstable 76Ga beam implanted in SSBD at low energy. 76Ga decays populating excited states of 76Ge, γ and β are detected in coincidence. Data: Total excitation energy and the probability of individual γ cascades for 76Ge. NLD γSF are then extracted via the Oslo method. A. Simon et al., Nucl. Instr. Meth. A703 (2013) 16 M. Guttormsen et al., Nucl. Instr. Meth. A555 (1987) 518

75Ge(n,γ)76Ge Results New NLD and γSF used in a TALYS nuclear reaction code significantly constrain the (n,γ) reaction rate from a factor of 10 to a factor of 2 uncertainty. This constraint will be even greater as nuclei further from stability are measured. Conclusion The β-Oslo method shows the potential to constrain astrophysical reaction rates for previously inaccessible neutron rich nuclei and as such can provide vital information for r-process nuclear astrophysics. . A. Spyrou et al., Phys. Rev. Lett. 113 (2014) 232502