The cosmic ray actinide charge spectrum derived from a [formula omitted] array of solid state nuclear track detectors in Earth orbit

Abstract

The DIAS-ESTEC Ultra Heavy Cosmic Ray Experiment (UHCRE) on the Long Duration Exposure Facility, collected approximately 3000 cosmic ray nuclei with Z>65 in the energy region E>1.5 GeV nucleon −1 during a six year exposure in Earth orbit. The entire accessible collecting area of the solid state nuclear track detector (SSNTD) array has been scanned for actinides, yielding a sample of 30 from an exposure of ≈150 m 2 sr yr . The UHCRE experimental setup is described and the observed charge spectrum presented. The current best value for the cosmic ray actinide relative abundance, ( Z>88)/(74⩽ Z⩽87), is reported.