Counting Radio-Krypton Atoms with a Laser

A study on 85Kr measurement with an internal gas proportional counter

A measurement method of ⁸⁵Kr using an internal gas proportional counter (IGPC) is presented in this study. The operation conditions of the IGPC were determined and optimized, including the operating voltage, pressure, sample volume, interference from other gas components such as nitrogen or air, and mitigation of the memory effect. The IGPC was calibrated using certified standards, and the detection efficiency was approximately 58% for typical samples. A lower limit of detection of approximately 0.11 MBq/m³(Kr) was achieved after counting for 5 h with 1 mL pure Kr, corresponding to the atmospheric activity concentration of 0.18 Bq/m³ (air). It was shown that the IGPC could be used effectively for measuring ⁸⁵Kr.

Development toward a double focusing isotopic separator for noble gas isotope enrichment

A double focusing sector field mass filter used in Nier-Johnson geometry has been built in order to perform Kr isotope enrichment for ⁸¹ Kr and ⁸⁵ Kr isotopes. The principle consists in implanting Kr⁺ ions accelerated at 7 keV in Al foils after separation using the magnetic sector. A specific ion source has been designed capable of generating high Kr⁺ ion beams (>0.5 μA) to transfer into the collecting Al foils in 3 to 5 h significant fractions of large Kr samples (10¹⁵ to 10¹⁶ atoms) initially introduced in the instrument. Implanted Kr isotopes can be further selectively released from the Al foil by surface ablation using an infrared laser beam. Implantation yields and enrichment factors are measured using a conventional mass spectrometer. Copyright © 2016 John Wiley & Sons, Ltd.