Cosmogenic Potassium in Iron Meteorites

Khan, Hammad (2022). Cosmogenic Potassium in Iron Meteorites (Unpublished). (Dissertation, Universität Bern, Physikalisches Institut)

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This project aims to reintroduce the 41K-K Cosmic ray exposure (CRE) age dating system for iron
meteorites. For this, very low amounts of potassium isotopes need to be extracted from the iron
meteorite. Attempts using chemical extraction methods, i.e., digestion of the sample, subsequent
oxidation of the iron, and finally separation of the potassium were unsuccessful. The resulting blank
would have been much too high for our purpose. Therefore, a more physical extraction system based
on the ideas of Voshage and Hintenberger (1959) was planned, designed, and built. The novel
instrument for the extraction of cosmogenic potassium isotopes consists of a Radio Frequency (RF)
heating coil, heating a metal crucible (Tantalum or Molybdenum). Inside this metal crucible there is a
BN or graphite liner to protect the metal from oxidation. The potassium, which forms positive ions in
the melt, is volatilised and electrostatically attracted by and implanted onto a negatively charged
filament. This filament is then used in a normal double filament set-up of the Thermal Ionisation Mass
Spectrometer (TIMS).

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