Commissioning of HECTOR at CASPAR

Orlando Gomez
Physics Graduate Students, University of Notre Dame

The High Efficiency Total Absorption Spectrometer (HECTOR), is a 4π γ-summing detector which specializes in measuring radiative-capture cross sections — e.g. (p, γ), (α, γ) — for reactions related to astrophysical processes. Last year, HECTOR was moved to the Compact Accelerator System for Performing Astrophysical Research (CASPAR) laboratory, which is located at the Sanford Underground Research Facility, 4850-feet underground. The underground environment provides an optimal background shielding needed to study several radiativate-capture processes at low energies related to the s-process. The commissioning of HECTOR at CASPAR, along with several measurements of resonance strengths below 1 MeV for the ²⁷Al(p, γ) ²⁸Si reaction will be presented.

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Using HECTOR for Capture Reaction Measurements Relevant to the Astrophysical p-process

Beka Kelmar
Physics Graduate Student, University of Notre Dame

Many open questions still exist in the field of nuclear astrophysics. One such question is the production mechanism of the 35 stable proton rich nuclei heavier than iron, known as the p-nuclei. One proposed mechanism is the p-process. The p-process consists of photo-disintegration reactions on seed nuclei created by either the r- or s-process.  One input that is important in the modeling of the p-process is the reaction rates for all of the photo-disintegration reaction that can occur. By measuring several (α,γ) reactions at the University of Notre Dame’s Nuclear Science Lab we are able to provide constraints on reaction rates relevant to the p-process in the A=100 mass region. These reactions were measured using the High EfficenCy TOtal absorption spectrometeR (HECTOR) and the data were analyzed using the γ-summing technique. By comparing the measured cross sections to various Hauser Feshbach models available in Talys 1.9 we are able to find the model combination that best describes the measurements and rates. We then examine the effect that these new constraints have on the predicted abundances of the 35 p-nuclei in network calculations.

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