Ultra-heavy cosmic ray studies with Ariel VI

The satellite Ariel VI was launched on 3 June 1979 into a near-circular 625 km 55° inclination orbit. The Bristol experiment on board is of a novel design using a spherical gas scintillation chamber with an integral plastic Cerenkov element¹. The data presented here were collected during an exposure of ~360 m² sr days with essentially 100% recording efficiency for events with Z>=38. The abundance spectrum, particularly for Z>=50, suggests that the cosmic ray source is significantly enriched in r-process material relative to the Solar System.