Study of nuclear reactions producing ³⁶Cl by micro-AMS

³⁶Cl is one of several short to medium lived isotopes (as compared to the earth age) whose abundances at the earlier solar system may help to clarify its formation process. There are two generally accepted possible models for the production of this radionuclide: it originated from the ejecta of a nearby supernova (where ³⁶Cl was most probably produced in the s-process by neutron irradiation of ³⁵Cl) and/or it was produced by in-situ irradiation of nebular dust by energetic particles (mostly, p, a, ³He -X-wind irradiation model).

The objective of the present work is to measure the cross section of the ³⁷Cl(p,d)³⁶Cl and ³⁵Cl(d,p)³⁶Cl nuclear reactions, by measuring the ³⁶Cl content of AgCl samples (previously bombarded with high energy protons and deuterons) with AMS, taking advantage of the very low detection limits of this technique for chlorine measurements.

For that, the micro-AMS system of the LF1/ITN laboratory had to be optimized for chlorine measurements, as to our knowledge this type of measurements had never been performed in such a system (AMS with micro-beam).

Here are presented the first results of these developments, namely the tests in terms of precision and reproducibility that were done by comparing AgCl blanks irradiated at the Portuguese National Reactor with standards produced by the dilution of the NIST SRM 4943 standard material.