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Abstract

The rare stable isotope 36S occurs on earth with an isotopic abundance of 0.015%. A further consistent abundance has been observed from the analysis of meteorites. Nucleosynthesis calculations, however, lead to a considerable overproduction of 36S, probably due to a lack of experimental reaction cross-section data. In the present work several (n,p) and (n,alpha) reactions contributing to the 36S nucleosynthesis have been investigated. In particular, the neutron energy dependent cross-sections sigma(p)(E(n)) and/or sigma(alpha)(E(n)) as well as the Maxwellian averaged cross-sections at kT = 30keV have been determined for 33S, 35Cl, 36Cl, 40K and 41Ca. A peculiarity of these reactions (except for 35Cl) is that the (n,p) and/or (n,alpha) cross-sections strongly exceed that for neutron capture, leading to another branch in the s-process. The 36Cl, 40K and 41Ca (n,p) and (n,alpha) reactions are also important in another respect since they affect the abundances of the potential chronometric pair 40K/40Ar. The measurements were performed at the Geel Linear Electron Accelerator (GELINA), which permits high resolution neutron spectroscopy in the keV-energy region. A dedicated set-up using a surface barrier detector or a gridded ionisation chamber was used. Great care was taken in the mass determination of the samples. Reliable values were obtained via calibration experiments with thermal neutrons and, in some cases, after destructive analysis of the sample.

Additional information

Authors: WAGEMANS C, University of Gent, Nuclear Physics Laboratory, Gent (BE);DRUYTS S, JRC Geel (BE)
Bibliographic Reference: Paper presented: 16th General Assembly of the European Geophysical Society, Wiesbaden (DE), April 22-26, 1991
Availability: Available from (1) as Paper EN 36087 ORA
Record Number: 199110856 / Last updated on: 1994-12-02
Category: PUBLICATION
Original language: en
Available languages: en