Sci Adv. 2019 Sep 11;5(9):eaaw5526. doi: 10.1126/sciadv.aaw5526. eCollection 2019 Sep.

Boutique neutrons advance ⁴⁰Ar/³⁹Ar geochronology.

Rutte D^1,², Renne PR^1,², Morrell J³, Qi L⁴, Ayllon M^3,⁵, van Bibber K³, Wilson J⁴, Becker TA¹, Batchelder J³, Bernstein LA^3,⁵, Lebois M⁴, James J³, Chong SA³, Heriot WL³, Wallace M³, Marcial A³, Johnson C³, Woolley G³, Adams PA³.

Author information

1: Berkeley Geochronology Center, Berkeley, CA 94709, USA.
2: Department of Earth and Planetary Sciences, University of California, Berkeley, Berkeley, CA 94720, USA.
3: Department of Nuclear Engineering, University of California, Berkeley, Berkeley, CA 94720, USA.
4: Institut de Physique Nucléaire d'Orsay, 91406 Orsay Cedex, France.
5: Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.

Abstract

We designed and tested a compact deuteron-deuteron fusion neutron generator for application to ⁴⁰Ar/³⁹Ar geochronology. The nearly monoenergetic neutrons produced for sample irradiation are anticipated to provide several advantages compared with conventional fission spectrum neutrons: Reduction of collateral nuclear reactions increases age accuracy and precision. Irradiation parameters within the neutron generator are more controllable compared with fission reactors. Confidence in the prediction of recoil energies is improved, and their likely reduction potentially broadens applicability of the dating method to fine-grained materials without vacuum encapsulation. Resolution of variation in the ³⁹K(n,p)³⁹Ar neutron capture cross section at 1.3 to 3.2 MeV and discovery of a strong resonance at ~2.4 MeV illuminate future pathways to improve the technique for ⁴⁰Ar/³⁹Ar dating.