The stable gallium isotopes, 69,71Ga, are mostly produced by the weak slow (s) process in massive stars. We report here on measurements of astrophysically-relevant neutron capture cross sections of the 69,71Ga(n,γ) reactions. The experiments were performed by the activation technique using a high-intensity (3−5×1010 n/s), quasi-Maxwellian neutron beam that closely mimics conditions of stellar s-process nucleosynthesis at kT≈ 40 keV. The neutron field was produced by a mA proton beam at Ep=1925 keV (beam power of 2-3 kW) from the Soreq Applied Research Accelerator Facility (SARAF), bombarding the Liquid-Lithium Target (LiLiT). A 473 mg sample of Ga2O3 of natural isotopic composition was activated in the LiLiT neutron field and the activities of 70,72Ga were measured by decay counting via γ-spectrometry with a high-purity germanium detector. The Maxwellian-averaged cross sections at kT = 30 keV of 69Ga and 71Ga determined in this work are 136(8) mb and 105(7) mb, respectively, in good agreement with previous experimental values. Astrophysical implications of the measurements are discussed.
@article{arxiv.2211.16774,
title = {Stellar $s$-process neutron capture cross sections of $^{69,71}$Ga},
author = {M. Tessler and M. Paul and S. Halfon and Y. Kashiv and D. Kijel and A. Kreisel and A. Shor and L. Weissman},
journal= {arXiv preprint arXiv:2211.16774},
year = {2022}
}