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NUCLEOSYNTHESIS 36,38Ar(n,g) REACTIONS WITH THE HIGH-INTENSITY SARAF-LiLiT NEUTRON SOURCE


  Moshe Tessler  ,  Moshe Tessler [1]  ,  Michael Paul [1]  ,  Tala Palchan [1]  ,  Shlomi Halfon [2]  ,  Leonid Weissman [2]  ,  Arik Kreisel [2]  ,  Asher Shor [2]  ,  Ido Silverman [2]  ,  Melina Avila Coronado [3]  ,  S. Almaraz-Calderon [3]  ,  Richard Pardo [3]  ,  K. Ernst Rehm [3]  ,  Daniel Santiago-Gonzalez [3],[4]  ,  Robert Scott [3]  ,  Claudio Ugalde [3]  ,  Richard Vondrasek [3]  ,  Mario Weigand [5]  ,  Tanja Heftrich [5]  ,  Rene Reifarth [5]  ,  D. Veltum [5]  ,  Roland Purtschert [6]  ,  D. Baggenstos [6]  ,  Philippe Collon [7]  ,  Yoav Kashiv [7]  
 [1] [1] The Hebrew University, Jerusalem, Israel
[2] [2] Soreq Nuclear Research Center, Yavne, Israel
[3] [3] Argonne National Laboratory, Argonne, IL, USA
[4] [4] Dpt. of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, USA
[5] [5] Goethe University of Frankfurt, Frankfurt, Germany
[6] [6] University of Bern, Bern, Switzerland
[7] [7] University of Notre Dame, Notre Dame, IN, USA

Neutron-induced reactions remain at the forefront of experimental investigations for the understanding of stellar nucleosynthesis and chemical evolution in the Galaxy. We report on recent experiments performed with the Liquid-Lithium Target (LiLiT) and the mA-proton beam at 1.92 MeV (2-3 kW) from the Soreq Applied Research Accelerator Facility (SARAF). The facility yields high-intensity quasi-Maxwellian (kT ~ 30-50 keV) neutrons (3-5×1010 n/s). As part of a program of neutron-capture measurements in the regime of the weak s-process, the 36,38Ar(n,g) reactions and their influence on light neutron-rich nuclides were studied for the first time. Gas samples were irradiated at the SARAF-LiLiT neutron source and the 37Ar/36Ar and 39Ar/38Ar ratios in the activated gas samples were determined by accelerator mass spectrometry at the ATLAS facility (Argonne National Laboratory). The 37Ar activity was also measured by low-level counting at the University of Bern. The measured values of the Maxwellian Averaged Cross Sections (MACS) are significantly different and lower than theoretical and evaluated data published so far, affecting the mass fraction of stable light neutron-rich nuclides up to 48Ti produced during He-burning of a massive star.

This work was supported in part by Israel Science Foundation (Grant Nr. 1387/15) and by Pazy Foundation (Israel), the US Department of Energy, Office of Nuclear Physics, under Contract NoDE-AC02-06CH11357. D.S.G. acknowledges the support by the U.S. Department of Energy, Office of Nuclear Physics, under grant No. DE-FG02-96ER40978. This research has received funding from the European Research Council under the European Unions's Seventh Framework Program (FP/2007-2013) /ERC Grant Agreement n. 615126.